I’ve seen this a lot as well. I have asked several of these persons why and the overwhelming answer is usually “I don’t want to just leave my belt lying around. It could get stolen or I might forget it.” Not fashion or function. Certainly this isn’t the case with every belt wearer but with most I have asked.
We teach our bodies to brace the spine by properly engaging the pelvic floor muscles and the transversus abdominus. These muscles hold our internaal organs in place and assist the body in creating the intraabdominal pressussure which braces the spine. Weight belts circumvent those mechanisms and our bodies, as has been stated earlier in this thread, become used to this external support. We should train (our) bodies to function correctly and use weight belts only those super max heavy lifts (which most people do not do anyway).