On buying used books. Or, phrasing it another way, how much of the market of random people selling stuff it controls.

Yeah its not like amazon, facebook marketplace, Craigslist, or literally millions of local marketplaces exist for this sort of thing

This. And also: if they don't exist. Open a new one! There is no law against it. And we would stand shoulders to shoulder if and when the government would ever propose such a law. But until that time, stop whining.