We tend to forget that the Klingons depicted on screen are a tiny percentage of an actual race. Not sure why congruence of all cultural ideals should be expected to be adhered to by every member.
Thing is, that tiny percentage of the overall population of the Klingons we saw were all their leaders and a notable group of Captans and commanders. So while we of course don't have a good overview how the vast majority of Klingon population dresses, we know how their leaders and notable character dresses and all "regular" people we saw followed that trend. So while it may only be a tiny percentage of the overall population, they very much stand in for the klingon "ideal" way better than theri actual raw numbers account for.