[lrvick]

The book that was scanned and shared with others, was also bought in the first place. Piracy sites are just decentralized libraries.

[condwanaland]

Yes, but these secondary markets have been fine because they still require a large primary market.

A library can only lend as many copies as it purchases. Someone selling their copy can only sell the copy they purchased. These secondaries are constrained by the primary.

Your talking about one person buying a single copy and then distributing it for free in perpetuity. This secondary is not constrained by the primary.