1. A Time Killer: Boredom is the most common problem of most people today. Dota can consume a lot of time without you even noticing it. You'll just say "wtf I'm late!" after the game.
2. Non-exhausting Game: Unlike Basketball or other physical sports, you can play Dota 'til you can still manage to sit, look at the monitor, use mouse and keyboard, and think. Yes, using your mind is also tiring but it'll take an average of 3 games before you'd want to take a rest.
3. Fame Source: Most players want to be the best in this game to gain fame which I find natural but technically nonsense. I have to admit that thirst for fame drove me to practice and improve my game. After getting the fame I wanted, I asked myself "Now what?". For players who don't plan on having Dota as their profession, Fame isn't that important.
4. Team Work Game: When we were kids we already love having team battles. That's why a lot of team sports came up and multi-player computer games have been invented. Playing with team mates is more addicting than playing alone.
5. Tranquilizing: Dota makes you forget your problems and make you think of simpler problem - how to win.
6. Non-violent war: We love wars. That's why there are shows like Wrestling, UFC, Action Films, etc. Dota is a chance to engage in wars safely. We can fight all day long and just stand up from our computer without even having a scratch.
7. Topic Provider: Dota is a great topic provider. That's why you talk about it while hanging out with your dota buddies. That's why there are forums and blogs like this. We love chatting and Dota is a great topic to talk about.
8. Sweet Sound Effects: "Rampage!!!" - How sweet that sound is? This sound effect is unconsciously a source of self-affirmation. Everyone loves to be praised and accepted. Dota can be a source of this.
9. Easy to Play: Survey shows that Dota is played by more people than other strategy games like Starcraft. One of the reason is it's simplicity. You only have to control one hero - a great news for people who are not into doing micros.
10. Total Freedom: In Dota, you have all the freedom to do anything you wish. You can gank, farm, lane top, lane mid, lane bot, buy items you wish, you can even annoy your team mates if you wish. It is like an alternative for people who doesn't that much freedom in their real lives.
11. Mind Exercise: Intelligent people love exercising their minds. This is the reason why crossword puzzles, Rubic's cube, and other mind games are created. Dota also have this feature needing analysis, prediction and decision making.
12. Physically safe: People care about their safety. In my case, I don't jump that much in Basketball because I hate landing on another player's foot and causing my ankles to be sprained. I don't want to try Rugby, Boxing, UFC and other dangerous sports because I care about my safety. Dota, on the other hand, doesn't offer dangerous injury. Eye problems may occur though but it's still avoidable. Just give your time proper rest and use low radiation monitors.
13. Game Variations: Every game is different. You buy different items, you lane against different opponents, you have different combos, you pick different heroes, you plan different attacks, etc. Variation is important to stay addicted on something. Nobody would want to do same things over and over again.
14. Source of Money: Money is becoming the goal of every humans. Poker won't be popular if you can't gain money from it. Dota have been used for betting games and tournaments; obviously, money is involved.
15. Ability to feel like having supernatural skills: We all love to have supernatural skills. In Dota, we have it. Just pick the hero that possess the skill you want. You want to teleport? You want to be invisible? Do you want to cast lightning on a person? It's all in Dota Allstars.
16. Tool for anger discharge: Dota can be the place where you release your anger. You can pick a killer hero, make it monster-like, then kill everyone you see.
17. Varieties of Skills to improve at: You can improve at farming, ganking, supporting, killing, teamwork, using different heroes, combos, etc. These are the things that will cause you to be practicing and improving. More skills learned means more addiction. More skills to be learned also means more addiction.
18. Character's Appearance: Dota Characters' appearances are made with great imagination. Dota Fan arts spread in the internet showing their appreciation in the Heroes' appearances. Cool arts and animations add to the addicting potion of this game.
19. Constant Map Improvement: Just when you learned enough strategies for you to be called a Dota genius, here comes another new map with new items and heroes. Now, your learned strategies need upgrade. You need to study, try and analyze new stuffs again making you more into the game.
20. Professional Gamers as Inspiration: Watching pro dota gamers execute strategies perfectly make you want to be like them. You will be training more after getting inspired by these Pro Dota players and teams.
21. Peer Pressure: Right when you don't feel like playing, here comes a Dota Buddy saying: "It's weekend let's play!" or while you're at home, you got a "Buzz!!" followed by the word "rak". How can you ever forget playing if these peer temptations are all around you?
22. Game illusion: While playing Dota, the map becomes your world and your hero becomes you. Feeling a different world which is more fun and breath-taking is way better than your old room with old stuffs. When the game's world is experienced, your mind would be constantly searching for that more pleasurable world making you really addicted.
23. It's haunting: This game haunts you. While you're in your classroom, you kept on thinking why you lost or how great your game was. You would then be thinking of playing Dota as soon as you arrive at the computer shop or at home. You would also think of what hero you would play or what play style you're going to have.
24. Winning Feels Good: Yup, feeling good is really addicting.
25. Losing makes you thirsty to win: On the other hand, losing is still addicting because you become more urge to have that wonderful feeling of winning.
26. No height or other physical disadvantage: In basketball you cannot have a team composed of 5 short players. In Rugby, you should be muscular. In Dota, you can be as thin and short as you want and still own everyone.
27. A balanced game: Since banning was introduced in Dota Allstars, I considered it to be a balanced game. Having a balanced game, you wouldn't think of quitting while whining "unfair!".
28. A vast number of strategies: More strategies means more trial and errors. More trial and errors means more games. "More games" means more game illusions. More game illusions means more chance to be trapped in the world of Dota.
29. Merely being a Strategy Game is addicting: Strategy games are so fun because it offers unpredictability.
30. No age limit: Yup, no age limit is a cause of Dota Addiction. Many players should be practicing their professions in real life but they are still stuck in Dota world.
31. Opportunity to become a Hero: It is so pleasurable to be feel like a hero. It is like hitting a buzzer beater in a basketball game or saving a kid from getting hit by a car. The appreciation is simply awesome. Self-esteem boosts quickly and exponentially with this.