Obsessive head skimming?

Everyone is always talking about skimming heads. As in the moment one comes off people seem to be on about slicing them.

Is this just some nonsense, or...?

I mean, if, for example, a plug tips come off in the head, and it has to be removed from an otherwise sound setup, what's the reason to skim it?

None....only skim it if its been roasted

skimming a head should only be done if necessary

Banana heads that have been warped by heat are the only real reason to do it (when I were a lad).
If the head is still flat and true, there's no need.

I once had 60 thou skimmed off a head.

Made 10bhp difference on a rolling road.