This has some psychological and biological reasons.
Apart from Sex drive, men are attracted to Breasts because of the fact that the first experience of a child is sucking the Mother’s breast.
The organism always resort to the first experiences of any drive/instinctive actions/reactions.
Men unconsciously finds solace in this, most of the time Consciously!
One may also note that at times of great stress one resorts to Sleeping in Fetal Position;this is the pose the child assumes when it was in the womb of its mother, where it felt it was safe, an instinctive reaction for survival
Why are Men obsessed with Breasts?
Here is the report.
‘Why do straight men devote so much headspace to those big, bulbous bags of fat drooping from women’s chests? Scientists have never satisfactorily explained men’s curious breast fixation, but now, a neuroscientist has struck upon an explanation that he says “just makes a lot of sense.”
Larry Young, a professor of psychiatry at Emory University who studies the neurological basis of complex social behaviors, thinks human evolution has harnessed an ancient neural circuit that originally evolved to strengthen the mother-infant bond during breast-feeding, and now uses this brain circuitry to strengthen the bond between couples as well. The result? Men, like babies, love breasts.
When a woman’s nipples are stimulated during breast-feeding, the neurochemical oxytocin, otherwise known as the “love drug,” floods her brain, helping to focus her attention and affection on her baby. But research over the past few years has shown that in humans, this circuitry isn’t reserved for exclusive use by infants.’