As a regular wearer of very very lowrise jeans, I never wear underwear as there just isn't room for it without an unsightly view of the top of them. It feels sexy to wear lowrise and it feels even sexier without undies. I am gay and I must admit that it looks sexy too when the cloth is thin and tight! Any other guys share this? ...Gary
Some of us older guys found the same problem maybe 40 years ago - but the lowrise jeans were then called Hipsters or Hiphuggers. The underwear available just did not match up to the new style jeans. Like you say Gary, showing a large expanse of underwear above the waistband is pretty unsightly (and that might be fashionable today but certainly not back then). I also found it very uncomfortable - being pulled in at the waist in two separate places, from the waist of the jeans and the waist of the pants. One day, on a trip to the coast, I could stand it no longer and went into a 'Gents' (restroom) and took off the baggy underwear and dumped it in a litter bin! Well, the jeans were pretty tight and didn't leave much to the imagination - but a young man might as well flaunt his assets.
You will recall that when hip-huggers first showed up around 1970, bikini underwear for men also made an appearance, in a manner of speaking, since it would show above the waistband of low on the hips pants. There were also shirts that were like leotards, that went between the legs, either fastening with snaps or something or all-in-one. I barely remember them. They were invariably trim fitting, going on tight, and of a stretchy material. The legs of the pants, with were referred to as either bell-bottoms, flared pants or even elephant legs, also tended to be rather tighter in the thigh than those today. So those making the fashion rounds today are not exactly the same. Very full pants called Oxford bags were also popular before WWII and apparently worn by high school and college age boys.
Another interesting note about those men's styles of the late 60s and early 70s is that they were being worn a few years earlier in Germany, as I noticed when I was there in the army.
Generally speaking, showing skin was not done with the low rider/hip huggers back then, for some reason. The styles for the tops were usually tight and worn tucked in more often than not. Tucking in your shirt was a big deal then. Not doing so was very rebellious.
In the 1970s dressier pants in polyester came along that could be worn as tight as you wished. If you wanted to show off your rear, male or female, those pants were the thing to wear. Higher waisted (actually worn at the waist) were available, too, and they were tended to be tight through the crotch. As you probably know, that produced the cameltoe effect for both men and women, though it looked a little different, as you can imagine.
I love wearing ULR jeans. Usually I wear non-stretch jeans, both tight and not so tight ones. I like to wear a top that just reaches the top of the jeans so that people people can see some skin as I move or bend over. I never wear underwear with my jeans. I almost never wear underwear with anything.
If I had the ideal for most guys - thick dark pubes, I'd luv showing them off. Alas, I have light, sparse pubes and thus don't have any need to trim. One of my favourite ULR jeans are Rufskin Hustlers, which show about half my ass crack. I have to add though that I feel most comfortable wearing them in gay venues.
I don't think you need small hips to pull off wearing low rise jeans, but if you have a HUGE ass and hips then you probably should avoid them because if half your ass is sticking out then it probably just increases the impression that you ass is too big to fit in your pants.
Underwear does not need to be worn with any jeans. I remember when Levi's introduced their low cut bell bottom jeans way back when. I thought it was terrible for anyone to allow their underwear to show while wearing them. I did not have this problem because I did not wear underwear anyway.
I saw a guy this week on Bourbon St. in New Orleans. Hi jeans were so low cut that his entire bush was exposed. You could even see the base of his dick. I know that bourbon is crazy place, but this was at 3:00 in the afternoon. Wow!