So's... like, everything in society, really. Capitalism itself comes readily to mind, as an extreme form of soft social control that's actually not all that soft at all, in aggregate.

In the case of clothing, marking willful non-conformists is, notably, a significant part of its true (as in: accurate and useful) signaling value. This is where some counter-cultural fashions come from, in fact—an effort to make it crystal clear that one is dressing contrary to fashion norms on purpose and not by accident. To signal a distinction between the non-conformist and the ignorant or destitute.