Men are always attracted to what is curvy on a woman and one of the things that they can't resist is a woman who have all the right curves in front of her. I have mentioned about this once in my posting but curvaceous women tend to attract attention, no matter her looks, her clothes or even whether she is sane or not.
I mean, of course, it does not mean all men will suddenly go mad or start chasing her like a scene from a movie, but the roving eyes will suddenly focus their attention on the chest region.
I think it is more of an instinct problem than just an attraction. Whenever men try to hide the fact they are looking, they will inadvertably look down and when they see the two globes which is naturally there, they will linger there a bit longer. At the risk of being caught looking.
And I myself would not be a straight man if I don't indulge in it occasionally. At the risk of being stared at by the woman and being given the look that says "Can't you look at me while I am talking and not my breast?".