I've been wearing one (with padding) for a while when I dress, just to present a convincing appearance. However, since going on HRT, I have started wearing a sports bra when I walk the dog (she's a greyhound, so it's an hour-long, vigorous walk!) to protect my nipples. They get pretty ouchy otherwise.
I might have to start wearing one at other times too, to avoid poking someone's eye out. Not that there's anything under them yet, but they sure are pointy!