It's probably because when we try to tone them down our guys look harder for them and then notice them moreI think it is normal for both men and women to glance and sometimes the level of cleavage requires a follow-up glance. I have large breasts and try my best to not make the glancer feel awkward about doing something perfectly normal and often unavoidable.
I do lean towards modesty by wearing a camisole under anything that might be revealing like a wrap dress. But even covering up completely doesn’t make my boobs go away. My husband noted that they are even more prominent when I wear a turtleneck. I can’t win.
One time I was in line at a convenience store next to an obviously intoxicated man that just stared at them. I mean like intensely stared. Then he slurred “nice shoes”. 🤣 That was the only time I have had anyone reach creeper-level looking but his comment made it a humorous memory.