[color=purple]I don't know about the folks lurking here. But, it's possible some of the folks just aren't 'into' typing. I have one brother who reads things on the internet, and e-mails sent to him, but he never responds to his e-mails because he doesn't type. He gets too frustrated with the hen pecking to type one word. I don't think this applies to most folks, but probably a few.
Another possibility, some of us are shy about initially joining groups (myself somewhat included, although I quickly feel comfortable once I'm involved). Even though an on-line forum is easier to join, shy types still feel like an outsider since they see friendships have already formed on-line.
Note to all lurkers: 
JOIN US...MOST OF US ARE GREAT FOLKS AND DON'T BITE!