At that point, why not just pirate and cut out the used disk middleman since the original creators aren't seeing any money from the purchase at that point anyway?

Lip service to the law, in theory purchasing used discs supports original sales of new discs, and I at least sometimes prefer the discovery experience of physical browsing.

Borrowing from libraries sort of gives money to the creators, since the libraries seem to buy + dump lots of copies. Buying used gives the libraries money, since they dump the copies at the used store.

Alternatively, be like me, and have a $100 budget for N ~= 20 BluRays/40 DVDs. 2-3 can be new purchases if used isn't in stock.