Gay guys are defiantly more open and honest about there feelings most of the time, but girls are more reserved so maybe that's why girls never come up to you. They might be afraid that if they say something you might reject them.
this isn't a for sure answer because I am not gay and also I am still in high school so its different but I have always felt that gay men can be attracted to men differently than women because they can have more physical attraction (they still have a Y chromosone) and also I feel that because gay men cannot always find other gay men easily so they find some cute that women won't because they see so many options in guys around them. A final maybe answer would be that they tell you because they know your straight and know that it won't matter much where as girls may be too shy to tell you because well some of them are like that while gay men know you won't go for them so they just be honest with you. These are jsut some ideas as I said I have no real idea haha