When I wore more slender jeans & slacks I did use a belt clip with the first flip phones I had (before that I had a big bag phone, mostly for the car, and the Army would give me a "brick" for my official travel).
The belt clip wasn't for prestige, but for practicality. With only 2 front trouser pockets the phone felt tight and made a big visual lump (is that your cell phone, or are yah just glad to see me?). Plus it competed with keys, loose change, and other items that could scratch it.
But today I'm retired in Florida and mostly wear cargo pants, short or long. And the phone goes into a big flapped pocket. Only problem is that sometimes when I sit in a car the phone wants to slide right out, despite the closed flap. So I always keep a grippy rubber protector on the phone, and that keeps it in place.