Something else to consider about those "irretrievable" coins: they may not be permanently irretrievable. As technology progresses, it may eventually become feasible to brute force the keys in a reasonable amount of time (although I'm not exactly sure how this would work, so I could be wrong).
It's not and never will be. It's not a matter of technology. There is simply not enough energy in this solar system to brute force private keys, even in theory.