As a gamer, a writer, and a sci-fi fan, there's lots of reasons for me to go to a convention. I've only recently begun playing Living Greyhawk, so you're likely to bump into me there. I also attend Renaissance festivals sometimes, when I get the chance. I sometimes make guest appearances at conventions, but honestly few people care to listen to me for an hour. On the other hand, I give out free RetroMUD stuff to anyone interested in RetroMUD. It's a great way to get free RetroMUD-branded merchandise and meet other RetroMUD players.
Actually, I do that so I can cover up the fact that nobody really wants to see me. They just come for the free stuff, which makes me look popular. I'll take it!