It's not just a matter of the belt warping or getting deformed.I only plan on carrying IWB. Does it matter much for those as well? I don't mind buying new belts everyonce in a while if it's just a matter of warping over time.
A belt designed for carry will hold the gun tighter to your body, aiding in concealment and very often aiding in comfort. You'll also be considerably less likely to find yourself constantly adjusting your rig or hiking up your pants because the cheapie off-the-rack belt can't support the weight of your rig.
I carried for a while with a fairly thick belt, but it was not designed for gun carry. Later got a gun belt from Crossbreed to go with my Supertuck. BIG difference.