1. They pay WGT for the advertising slot on this site.
2. Many of them do work. I've found over the years that only one or two companies are really trustworthy (to me); those are the only ones I try. Some people have luck with others. If people quit trying the scam ones after the first attempt or two those companies will go away when they are no longer getting any information for their advertising dollar.
It has gotten to the point where WGT might want to put a rating system in place for survey companies like they have for some videos.