If you'll make a game, record a movie, write a book etc., it's up to you if you release it for free or not. Same with trainers. Someone wants to make some profits for his job. I'm not saying it's good way to make money, but it's up to him if he wanna share his tool to everyone without any fees or not.
And if you started to play FW because of free trainers, well, I'm sorry about you.