Do we not know who we are?

Let me start by saying that this post is not intended in any way to be political.

Seeing my neighbour putting a UK sticker on the back of his car made me wonder why we have changed from GB. For as far back as I can remember, (and I'm now 75), and before we were in / out of the EU or its predecessor,  vehicles have displayed a GB sticker when going overseas but now we have a sudden change to a UK identifier. Why?

As a country ( and I use that word in its broadest sense),  in recent centuries we have been know as Britain, Great Britain, the British Isles and the United Kingdom as well as the more specific England,  Wales, Scotland and Northern Ireland with the inhabitants of those countries being referred to as English, Welsh, Scottish and Irish, not United Kingdomish. At the moment, with nationalism in the various countries being promoted by sizeable numbers of residents it seems to me that we are anything but a United Kingdom. So this brings me back to the original question, why change vehicle identifiers from GB to UK?  If we are now beholden to no-one except ourselves, why change? It seems to me that we don't know who we are.