Insofar as laundry is concerned, some men are not very detail oriented and could not possibly care less if their colors bleed or if the polyester or finer cotton gets pills and pulls because it rubbed against the denim in the washer or dryer. Heck, there is probably even a few who don't care whether the stuff they wear is clean at all. Somehow I imagine that they know what color that shirt or those underwear are ... they just don't particularly care about separating them.
My comment about laundry was more for the married people. My wife and I have discussion on what is light and dark all the time.