Why to wear a bra ?
Nipple poking.
My wife "technically" doesn't ever have to wear a bra - for support. But if she's wearing a thin-fabric top, her nipples poking make it obvious that she's braless.
In the winter she prefers to wear one because it helps keep her warm. But in the summer, whenever we get ready to go out and she's braless, she'll ask me if her nipples are "showing" too much. She does have tops that are thick enough to conceal her nips.
But when we go to the resort she doesn't care because - obviously - because she's on her way to be naked anyway.
I don't think "Yes" could ever be the answer to the question "Are my nipples showing too much?". They're only natural and I've never seen one I didn't like. Perhaps prints are the answer for thinner fabrics as they would be less obvious.
My wife is afraid that someone will see the outline of her breast.
She even usually wears one if our adult son is home.
I told her that an adult male is unlikely to notice his mothers breasts under her shirt, but she still wears a bra at home, even though she complains that they are uncomfortable.
She has no problem being in her modest nightwear at home even when he is around.
In fact, when I was starting to be nude more at home and he was not around (and was then a child), one of my lines was "Since you're in your sleepwear I might as well be in mine" and proceed to take off everything but my wedding ring.
Di hasn't worn a bra in decades. She used to wear underwire bras for support, then went to wireless. After a few scary incidents with fibroid cysts and them being removed, her doctor told her to stop wearing bras. Since then, and only when she feels she needs to, she's worn bralettes. Much like a sports bra but less confining and constricting. We find them while out shopping. Some are Lycra based and some are mostly cotton. It's like wearing a tighter t shirt.
Di is a C cup. Going braless is not an issue with her. What's at issue is that she's a private person. She doesn't like to be center of attention, doesn't like being watched. With her C cups breasts and the amount of jiggle, wiggle, sway and bounce she does, when braless, it attracts attention she is uncomfortable with. Di has ample size nipples. They are big, they aren't small. They do, however, become erect quite often and it doesn't seem to bother her too much until she catches men and women staring at her breasts.
If we are vacationing away from home, in a tropical setting, Di won't even pack bralettes. She's comfortable on vacations away from home going braless and without panties. Anywhere where we might run into someone we know, even if there's a remote chance, she's got her bralette on for sure. Summer is around the corner and its sundress season. She's quite comfortable wearing her sundresses without a bralette and most times without panties.
I don't know where to find it, but I did a post about wearing bras. I had copied an article that said bras were unhealthy. They can make you sick. My wife would go without her bra often. If I did not recognize it, she would sit down by me and nudge me, until I figured it out I liked to play with her nipples through the fabric. My sister Kay, does not like to wear a bra. My solution for nipples showing would be pasties. You can get some very cheap.