I haven’t seen it a ton. I do see a couple wear them during the proper belt wearing lifts (squat, deadlift, row, OHP).
We got one kid with some real potential. 16 years old, about 6’ @ 170. Got a 585 deadlift to mid thigh this last Sunday. His older brother pulls 800 lbs though at 220 lbs at around the same height, so they are mutants.
My gym is primarily powerlifting, strongman, college athletes, so that may be the difference.
The gym I use is a leisure center connected to a school and they all come in with so much equipment I barely even know what half of it is used for. There’s currently a trend where they all use slingshots for their benches 4x a week, usually just before using smelling salts to sumo deadlift 120kg with a belt on.
Don’t get me wrong, some of them are legit machines and if they stay injury-free and are having fun, all the best to them. Maybe i’m the loser though because I don’t own a belt and haven’t even considered using one yet.