I think used bookstores are a boutique industry only suited to larger markets. When I lived in Mississippi from 2001 to 2012, there were almost no used bookstores anywhere. Oxford (home of U of Miss) has a very famous one, but Starkville (home of Miss State U) has none; we had to drive two or three hours to Oxford or Memphis. Jackson, the state capital, didn't even have one that I was ever able to find, and neither did Tupelo, Meridian, or Hattiesburg.
What were more common were book exchanges, where you would bring three books and then get to take one for free. The economic benefits for the customer never made much sense to me, and I always found the selection less interesting than the used bookstores--mostly supermarket romances.
Around 2010, the Barnes and Noble in Starkville, which had only been open a year or two, cut its non-textbook inventory fully in half, and replaced the space with MSU hoodies, sweatshirts, and cowbells. If there is any place that needs LESS cowbell, it's a bookstore. But, they need to sell what makes them money.