Idk, I almost exclusively wear briefs similar to those in my pic (if not, then a thong). I think more guys would wear them if they didn't perceive others would judge or if they didn't feel insecure in them.
I've noticed when in college locker rooms, some would feel uncomfortable showing their briefs and have their shirt over them, but if I was open about it they'd loosen up and be in theirs.
Also noticed that briefs were more popular in college than in HS, maybe due to the fear of judgment being less but also maybe because clothes starting getting more streamlined in the early/mid-2010s.