If you want men to approach you, how about making the first move. Like give a hint (how subtle depends on you) to let them know you are available and willing to mingle. Or you could completely skip past the hinting and just approach the men you want to be approached by. Be forward, men like not having to chase at times.

As to why you aren't being approached, I can't tell from your brief descriptions. If i were to make an educated guess maybe it's because they are intimidated by how attractive you are. Maybe it could be the fact that you have an inapproachable vibe about you. Maybe they think you are spoken for already. The list is endless but those could be some.