When did it become o.k. to...?

Can someone please tell me when it became o.k. to wear undergarments as tops ala Rachel in Friends? Having been going out and about more often than I used to (something about being single again makes you do this), I've been noticing that some women have been wearing what I would consider to be frilly undergarments, putting on a bra (or in some cases not), and that's all. No jackets or anything else to cover up their barely covered bodies. This really isn't a complaint per se (if you want, go nude for all I care, but be prepared for the consequences), but this being the Bible Belt and all, I didn't think I'd be seeing this type of fashion here. This is what I'd consider normal in a "red-light" district, not Farragut. Maybe I am getting a bit more conservative in my old age of 35 (I hope not!).

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