@Hungrylm Probably because a great deal of bl/gl/yaoi/yuri is aimed at straight people of the opposite gender, basically fetishizing homosexuality instead of depicting more realistic scenarios including the societal troubles they face. There are manga/anime with good/unfetishized depictions of homosexuality, but they are few and far between, and thus unlikely to affect the general opinion.
(Here, I could go into a rant about how the fetishizing is actually damaging to how homosexuals are percieved, due to the implied objectification, but I’ll spare you the rant, as it would just be my conjectures and I am by no means an expert in Japanese sociology, thus ending up at my original stance that it’s at least not a major positive force.)
(My #1 recommendation is Shimanami Tasogare/Our Dreams at Dusk, it really is great. Bloom into You is also fantastic, but perhaps as much for the romance in general, which weakens it as a contender (for the #1 spot).)