I need to start by saying that I totally and completely understand, and wouldn't begrudge you the decision to go without one. They look like they could be hugely uncomfortable. The jockstrap thing is a non-issue, also: they aren't that uncomfortable to a lot of guys, especially those who wear tidy whities, and balls go south regardless...just like boobs. Still, your point is valid and taken.
Having said that, I have to say that I LOVE bras. I mean, I love a woman in a bra and no blouse. I think a lot of men do. They're a kind of peekaboo device, and one of those reasons that men read the Vicky's Secret catalog 10 to 1 over women - it's a turn on. Flowery, lacy, sheer - whatever. Guys are visual. Bras can be sexy.
Other than the peekaboo thing, though, I have no idea why.
Counterpoint: I like, equally, the look of bralessness under a blouse. Again, it's a peekaboo thing, very sexy, all that jiggle and little poky looking bumpy and pointy parts.
What the fuck is wrong with men? Why are nipples so damn cool? Boobs, functional devices when feeding our young, can cause men to salivate and shiver and become erect just by looking at them. I am not immune. Wierd. Just wierd. Whatever.
For you, I say "more power to you."