I came here back in the early 2000's when I followed a thread from the WotC D&D boards. I lurked for a year or so before finally signing up.
I stuck around for a few things.
1. It gives me a D&D fix. When I first came to EN World, I didn't have a group and hadn't played in a regular game for a couple of years. Posting on EN World at least let me talk about D&D and other roleplaying games, even if I wasn't getting to play in one. Now that I have a regular group I can still use EN World to give me a session-to-session fix.
2. I find a lot of the topics interesting to read. This has probably died off a little since I don't currently play 4E, so the "latest product X" threads no longer hold much interest for me. There are still some threads that grab my attention though.
3. I can discuss any issues I have in my game. This has died off a bit too since my game is going really well. I know that EN World is here if I need it for that though.
4. The latest news on D&D and other RPG's. EN World is always a great source of information for what's going on in the hobby. That's what it was when it originally started, and it continues to be today.
5. Rules queries. Even though I don't play 4E, the 3.Xe Rules Forum is still a great information source for any rules queries I have. The traffic isn't as much as it used to be but I can still generally get a few people to answer my question.
6. The community. Over the years I have come across a lot of awesome people on EN World. The overall vibe here is a lot nicer than many other internet forums I have used. I have never met another EN Worlder in person but, despite that, I have benefited from the generousity of several EN Worlders. You don't find those sorts of people just anywhere on the Internet.
Olaf the Stout