If our goal is true anonymisation, that is, even the host cannot know who the data belongs to, why are we hashing data at all, and not completely removing it?

If our goal is true anonymisation, that is, even the host cannot know who the data belongs to, why are we hashing data at all, and not completely removing it? Replace the pii (name, email address, phone etc) with a fixed number of *'s. There's no reversing or guessing that. If we are wanting information to be readable by some people in some circumstances, that's not anonymisation: that's data protection and an entirely different problem.