Anything with a zipper like that, is a sexual statement. Whether the girls know it or not. Guys are thinking, boy, how easy would it be, to reach over and pull down the zipper? So tempting! Knowing (well, assuming either rightly or wrongly) that she isn't wearing anything but a bra underneath. In one smooth motion, you could be seeing the whole bra, not just tantalizing glimpses. Or, if the girl is more adventurous, bare breasts. I'm telling you, shirts that zip....particularly but not necessarily if worn in a provocative way, are intrinsically sexual.
Do the girls know this? Some of them must. Especially those who wear them in a provocative way. Do all of them? Do they know what a furor they are causing in the mind and the ah....pants of every guy who sees them? Well, maybe not every guy. I shouldn't assume. But certainly a majority. And if you're a girl who didn't know this before but knows it now.......I implore you, don't stop wearing them! Embrace them, buy more, wear them more often. It's a good thing.