The problem with branch closures is - for me anyway - that you lose the ability to do the uncommon tasks face to face. The basic functions can be done at the Post Office, yes. But opening accounts can be trickier, and you don't have a human to talk to face to face when things go wrong.
The two things that drove me into a branch recently we're opening an account for my son (impossible to do all the steps online) and resolving a problem with a missing replacement debit card (which seemed to go very wrong.)
Yes I could have done the latter via the call centre but I have never used telephone banking, have no idea what my security details are, and so on.
That's the kind of problem to resolve