Um I wouldn't say that as a straight woman I am fascinated by other womens breasts. Breasts are completely natural to me. There is no shame about them but nothing exciting either. Maybe that's it. Because we don't get excited or stimulated by breasts we feel perfectly comfortable to talk about them all matter of fact like.
However my boyfriend and his mates do talk about the size of their 'floo floos' and what not. I asked him what the go with that was and pretty much got the same response as I described above.