Cryptocurrencies in general are quite difficult to kill and seem to be the digital equivalent of space junk https://en.wikipedia.org/wiki/Space_debris. Proof of burn would be a novel way of cleaning up a ledger. With a smart contracting system like Ethereum, you could also issue a token to be used in the burn contract to cover the set who have lost their tokens. There's honestly a lot of flexibility and it more depends on exactly what your goal happens to be.

I think proof of burn is most effective when one wants to change the social contract of the system. It's the ultimate form of consent because you are forever destroying your ownership in one system for another.