What is the psychological reason for why some Women love to show off their breasts while others want to hide them?

Before anyone says "Mine are large and I don't have a choice." I understand that, but I still know that everyone has a choice of wearing something low cut or not low cut. I know this because I've seen pictures and videos of some of the largest breasted models on youtube, and other places posing in both low cut and even covered up completely. Yes you can still tell they are there, but there is no skin and cleavage showing. I'm not complaining about this but as a man who is attracted to large breasts, I'm curious about this.

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7 mo
I wanted to tell my story a bit.

When I was in Middle School, some girls tried to wear low cut tops, and a teacher told them to change. When I was in High School, there seemed to be certain days when lots of girls would wear low cut tops. It always seemed like they tried to get by with wearing the bare minimal required by the school dress code. I don't think showing cleavage is ever necessary unless the woman needs to cool down her boobs.
What is the psychological reason for why some Women love to show off their breasts while others want to hide them?
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