As I often do, I'll start with a brief history. Underwear was first worn, not to protect sensitive parts of the person from the rough woolen clothing, but rather to protect the clothes from the person! Well at least that's the story in Europe, I have no idea what they did in Asia, North America or the Middle East. Or older civilizations for that matter. Did Romans wear underwear underneath those togas? Who knows. Anyways, back in the medieval period of Western Europe, people didn't have much in the way of clothes. They pretty much had what they wore, and nothing else. And so they would wear that stuff all the time. And when I say all the time, I mean, for years and years. Pretty much until it fell apart I guess. And was impossible to sew back up. And they didn't do much in the way of washing either. They didn't wash their clothes, and they didn't wash themselves. I believe that one bath a year was about average for most people. So they wanted to protect their clothes from various dirty dangers from their bodies. I suppose this applied more to nobles, richer people who had clothes that were actually nice, that they wanted to protect, less so for the common farmer. So that was the beginning of underwear.
Before that, who knows. I believe that some civilizations wore bras. I read somewhere that there was some culture -- fluorished about the same time as the Greek glory period I believe, that wore bras that pushed their breasts out so far that they looked like horns. Or something like that. I have to assume that other cultures existed who wore forms of underwear. But getting on with it.
I guess at some point, cleanliness became more regular, and underwear began to serve less to keep clothes clean, but to protect people from clothes. Like I alluded to before, those woolen pants must have chafed! I imagine at some point, underwear became an accepted part of society, then a required part of society. Womens' underwear became incredibly elaborate -- and painful no doubt. This is the period of the whalebone corsets and bustles and who knows what else. I'm no expert. I have seen pictures of how the damn things were so tight that the internal organs of women were rearranged though. None too pleasant.
My history of underwear is falling apart. I need to do more research. Anyways, mens' underwear went from I think longer jockey short type stuff to briefs, around the turn of the century. The modern "let me hold my boobs up with my shoulders bra" replaced the old fashioned "let me push up my boobs from my hips corset" in 1912. And underwear has remained largely the same since then. I suppose. A lot of women didn't wear bras for awhile in the 1960's. But that was an aberration I think. I once read part of a book about the history of underwear. I think it's time to revisit it. These are things that everybody should know about.
Anyways, so here we are, everybody wearing underwear. A legacy of the days when we had to protect our clothes from our bodies. So the question now is, is it necessary? From society's point of view, underwear is a must, there's no doubt about that. It's just one of those things. If you tell someone you don't have underwear on, and they'll think either you are a lecherous/slutty person, you're totally disgusting, you're weird, or they'll want to screw you right then and there. You won't get many people to react without surprise, and without strong feelings of some sort, generally negative. This is (at least I think it is) a phenomenon limited to North America. Or at least it's much stronger in North America than in the rest of the world. That Puritan aversion to acknowledging the part of your body between your waist and your knees again. So society says yes! A neccesity!
How about physically? I believe that most people generally don't really need underwear. I mean as long as you bathe yourself and your clothes regularly, cleanliness shouldn't be a problem. As for protection, it's probably better for you not to wear underwear. With underwear, you create a cramped damp atmosphere....perfect for bacteria to grow. Without underwear, you get a lot more air circulation, thus preventing infections. I can see where underwear might come in handy. Doing sports or other strenuous physicaly activity for example, it's usually easier to keep everything tucked in (although I don't know how much of a difference it would make for girls). For girls, it would be handy I suppose to have some underwear on during menstruation. And a bra would be good too while doing physical type stuff. And I guess that for bigger chested girls, a bra is a good idea just during normal times. I've heard that it can hurt if you don't have one? How did you girls manage back in the caveman days when bras weren't around?
So my proposal is this. Let's eliminate all forms of underwear as a societal necessity. Wearing it for practical physical purposes, no problem with that. Wearing it just cuz you like it, that's cool too. But let's make it so that if you don't wear it, you're not weird or disgusting or sexy or whatever. Just normal.