Possible? Yes, no doubt, lots of the users here earned on Services board.
because I think most people do not want to buy a service from this forum.
Give us stats or any interviews, thoughts about your claim. Because if what you think is true then you will not see any threads there posting their services.
Just take note that buyers dont just take a look on this forum, many visits and buy on other popular freelance websites because of cheaper rates and etc.