Guilds, some things I've pondered about.

When i was lower leveled, i joined because i can't play alone. I usually stayed in one guild (Tehsmecks) in windia, and most of my friends came from there. A few guilds later i found myself world xferring to khaini to be with my best RL friends (3 of them), and it was fun. After they all quit shortly after i xferred i wanted to join a much bigger guild of higher leveled people so i'd have more fun meeting people and make it easier for me to get zhelms and other stuff you need a group to get.

I guess in a nut-shell, early on i do it to meet people had have some fun. Later on i do it to meet people and make getting things easier.