I think some guys are scared to approach in the light of the .. #metoo .. movement for fear women will take their usual banter as some kind of harassment. Casual flirting, if pleasant between both parties and has a give and take is not harassment and women can tell the difference so it might not just be something about you it could be the nature of the world now. Are you seeking male attention, are you a talk to people you barely know, do you flirt, make eye contact? I never had guys hit on me in my late teens early 20s but it was mostly because I gave off the vibe off don't try I am taken, I wonder what vibe you could slightly give off if you think it may be something you yourself are doing to keep men away? Why not take control and if there is a guy you know that you like and know he is single, ask him out, why wait for them to ask you? You pursue, not wait to be pursued.
“Accept — then act. Whatever the present moment contains, accept it as if you had chosen it. Always work with it, not against it. Make it your friend and ally, not your enemy. This will miraculously transform your whole life.”
― Eckhart Tolle