Ask HN: Why Prefer Blockchain over Distributed DBs?

As an engineer myself, I haven't been really able to understand what advantages do blockchains offer over general distributed databases? It can be lack of knowledge as well but to me blockchains just seem like extremely inefficient form of DBs

The only comment I have seen is that they allow decentralization. But then why would it make sense for them to use for private companies, banks etc. ?

Note than I am not talking about Bitcoin, Ethereum etc. I am more interested in the basic tech on which these platforms are built.