Boobs....

Its pure and simple...

It really goes back to raising a family and its one of the other things males look for in a female to raise our off spring. See as males we look for a female we figure can best raise our kids. Thats why we dig the hips - sign a female can carry a child to term, butt - heck i dunno why we do, we just do, chest - able to feed our childern and that shes generally in good shape.

Now granted we are far from needing a big chested, wide hipped female to raise our kids these days, but that little bit of programing is still alive and well in alot of us. Granted some of us dont see a females chest as the most important thing and that means something else catches our eye first... and that is another topic in itself