I know, but I think they refrain themselves from making it because most of the yaoi manga is too raw and I'm guessing going to be too censored to make an anime. For example I remember watching sekaiichi hatsukoi and in the anime they censor most of the sex scenes that are in the manga, or they change some of it, like in the anime it doesn't show a certain blowjob scene that would be in the manga. (sorry its so long)
There needs to be more Yaoi / shounen ai anime's there's so many mangas that I would like to see animated #-.-)