Why am I so obsessed with girls butts?

I've always been a man who likes the rear end of a girl. It seems like the older I'm getting the more obvious I am in public. I'm pushing 60 years old and I still have the ump and desire for women. I'm a firm believer that looking at a pretty girl is alright, even if it is with bad intent. I'm I wrong or I'm I normal? I think I'm just fine- but that's me.