IMO, most people don't think long-term enough for market forces to be sufficient to solve lifestyle or resource allocation problems.

Unhealthy foods, bad television, alcohol abuse, water rights, sportsball conspiracies, downvote retribution -- really any personal choice that can be made wrongly by a weak-willed mortal meatsack -- are going to require violent (hopefully abstracted and implied violence via government, rather than direct violence in most cases) intervention to solve.