Also, it’s possible that (far) in the future, computing power gets sufficiently advanced to break private keys. The network would move to a new cryptography scheme at the first hint it was possible, but “lost” coins wouldn’t be moved, and would end up being “salvaged”. 

Much like much like a 1600s sunk pirate ship filled with gold. That gold was likewise “lost”, but now we have the technology (submarines) to  retrieve it.