Why do older guys like me..........?

okay im 12 and everytime i go to like a football game or bowling,skating ect. i always get like 15 yr old guys hitting on me like they will stare and things like that and theyll come and talk to me and stuff.....im tall like 5'6 but they know im 12 cuz i tell them but they keep doing it.....but what is funny is that guys in 7th and 8th grade dont like me at all only 9th graders and stuff i mean i have and suff but i dont have a big but i do have long legs. ......WHY IS THIS