OK, to be able to answer this question myself we must go back in time a little. When i was 5 i was molested by a guy so reading normal straight romance manga/anime reminds me of being molested. But when i read yaoi it doesn't reminds me of it and i'm able to feel that pleasure (not the horny lewd pleasure ⁄(⁄ ⁄·⁄ω⁄·⁄ ⁄)⁄ ) when reading romance mangas. I guess that's my reason(?)