I think I recall another thread about this I may have posted too, and another wrestler on here I seem to remember has commented on the bikini brief topic too. So some of my reply may be a repeat.
But yes many straight guys wear string or bikini briefs. All the way back to when I was in high school when is seemed some guys viewed bikini briefs as a viable alternative to a jockstrap, this was mid 90's.
I see Rugby players wear bikini briefs, usually thicker more durable ones either in place of compression or even under compression shorts. This seems to be OK with Rugby guys because a lot of photos you see of Rugby players in different countries, when the shorts come off that is what they wear.
Have seen several basketball and soccer players use these as support, especially the string bikini variety, as support since they think a real jockstrap is too old school. But for soccer they end up changing on the bus a lot and don't have a locker room of their own in the high schools around here so I kind of understand even if changing into a jockstrap on the bus wouldn't bother me, I know it does some of them.
Around 2010 I say a big increase in bikini briefs in the wrestling locker rooms, that was when the rule changed that they can no longer weigh in naked or wearing only a jockstrap. Both front and back have to be covered even if only skanlty.
I went through a phase of wearing them early in college as underwear after being introduced to them by a dorm mate. I like the lack of fabric, especially good on a date!!!! the dorm mate used them under his cup and jockstrap as well a using them as regular underwear.
On a recent note, I was helping my current girlfriends teenage son move and re arrange his bedroom. His mom had also told him to go through his clothes and bring out anything too little or he wouldn't wear anymore. One thing in particular was his underwear drawer, which had gotten to the point of taking of two large drawers. when he dumped them out on his bed.. a few notable things I noticed..........
He has always been pretty open with me, almost enjoying having a brother or male figure to talk to or even brag too and sometimes confide in. So it may for an hour of interesting conversation.
A youth UnderArmour cup which he seemed to enjoy making sure I knew he could not even come close to fitting into anymore.
As he ws slimming it down the first thing he did was to remove all boxer shorts and box them up keeping only a couple pair he grinningly said might be handy for hangin out at his GF house.
Next he sorted out 3 of the jockstraps with the football pads attached to them. 2 of them he had gotten at school and the other he had ask me to help him order online, it was a Nike version which is hard to come by.
He also hada few regular jockstraps which surprised me since while I had been encouraging him to wear but he had never stated he would or was. He saw me looking at them and readily told me he had gotten them from the supply at my school and hoped I was ok with it, I was and really glad he took it on himself to do that.
But the last thing I noticed was 3 pair of FOTL bikini briefs. He picked them up and seemd to need to explain them telling me he had gotten them to wear to hold things better when he used to play basketball and even wear them under his regular football girdle since they don't hold much sweat.............basically one reason I had given him for trying a jockstrap.
He didn't remove them from the underwear he was keeping.
Basically he was left with those bikini briefs and 30 pair of all clingy snug fitting usually short leg boxerbriefs and trunks.
He put all the jockstraps and gridle with is other sprots specific stuff in a drawer of their own.
Kind of neat seeing a guy go through his underwear drawer?