My reasons for frequenting two science forums and a chess forum are as follows:
1.) My personal schedule is erratic and precludes much social interaction in real time, beyond work. The forums are available 24/7/365, or almost so, depending on the ISP.
2.) There is great diversity available in topics and personalities posting. I enjoy being able to to choose among such a rich tapestry of offerings and potential.
3.) Though I do not have much hard science to contribute, I am generally regarded to be observant and possessed of adequate communication skills. I come to share these skills and to improve them through interactions with others.
(As an aside, I wonder if Oli has a good recipe for Duck a l'Orange? I have a sense that he may be an Epicurean.)