A criteria for when a woman needs to wear a bra is when you can keep a pencil from falling under your breast.
Due to aging, being on the heavy side and body changes (genetics playing a part, the women in my family tend to be big breasted) I can pass that test. Unaided I can fill a C cup bra easily. Under a shirt with no bra on it isn't too noticeable but with a polo or golf shirt they are more obvious.
I know a bra offers support but it also obviously shapes them. En fem its an asset, in drab its a problem. I know there are members here that have the same issues and some wear bras on a regular basis. What are the reactions that you get and what do you others handle it.