Thrilling, but sort of in reverse:
We have newish neighbors. Huge age spread (wife is 24, husband is 45). When they moved in a few months ago, I noticed that the wife was braless. And every single time I have seen her since, she is braless. C-cup, semi-droopy boobs, just perfect. They jiggle with the breeze, even if she isn't moving, I swear. She is rather petite, yet still has curves in all the right places.
Yesterday morning, I noticed she was leaving with her husband and his dad. She had a bra on!
Later that evening I was hanging out with them outside and she still had her bra on. They mentioned that they had spent the day with her father in law.
I just found it rather exciting that I see them come and go all the time and talk to them in person every day, and she is braless, but around her father in law she wears a bra.
It makes it exciting that she doesn't care that random people see her braless and her neighbors see her braless, but around certain people she makes sure to wear a bra. That also strongly implies that she is well aware of what the rest of us get to see on a daily basis.