Maybe it's just me, but I thought your boob size only indicated how big your boobs were.
Yet, people seem to think that women with small breasts are more likely to be hard-working, moral, and modest, while women with large breasts are more likely to be popular and sexually attractive. That's not awful, but breast size is also often associated with intelligence. Specifically, smart girls have small boobs and dumb girls have big boobs.
Surprise! Breast size is not actually correlated with any of these traits.
If you're making assumptions about who people are based on what they look like, stop. Seriously, stop.
But you don't have to take my word for it — or the word of the Cultural Encyclopedia of the Breast (which is a real thing). Here are a bunch of stories of real women who were treated like they were dumb solely based on their cup size.