Is there some reason to do this other than ideological protest?

For US citizens there is the global taxation rules. Is there something like that for UK citizens?

[delayed]

To the sibling comment: It's in case you wish to acquire citizenship in another country that does not recognise dual citizenship.

I.e. that [new] country will not allow you to become a citizen of it unless you renounce your original one.

What that might actually mean practically, or if you can un-renounce it later, I don't know. [Edit]: Turns out, according to that page, yes, you can do that with some kind of bureaucratic shuffle. Daft - but sometimes these things are.