Most forms of entertainment – without leaving the house – aren’t social in nature: watching TV, reading a book, playing single player games, etc.

Online games free players from geographical and spatial constraints, and puts like-minded people together on the same server, world, instance or whatever.

You are entertained and you can socialize WHILE remaining entirely within your physical and social comfort zones: no need to leave the comforts of your den, and no need to deal with the pitfalls and occasional awkwardness of face-to-face interaction.

It’s addictive, because it’s also the path of least resistance that’s available 24/7.

It’s addictive because it’s so easy.

For many, online games start to replace more ‘difficult’ activities, such as inviting friends over for board games or dinner and drinks, or even just interacting with family members (but we all know that family isn’t really entertainment).

TLDR version: MMOs and online games are attractive because they’re *easy* to indulge in.

Personally, I prefer having fun in the old-fashioned ways.