Even a fairly light handgun will curl a regular dress belt.
Add to this a phone holder and some other things like a knife in a holster and maybe a pepper spray holder and you get enough weight to ruin a belt.
Worse yet,when the belt curls,you start dropping stuff all the time.
It's a massive pain in the -you know-.
Starting with a belt strong enough to maintain it's straightness means you have one less thing you have to worry about.