Okay, fair point, they might just re-include the UK in whatever exclusion list they have and that'll be that. But since GDPR came into force, others have followed suit, several other countries have begun implementing similar legislation.

This is anecdata, so fair warning, but over the last year (at a guess) I've noticed many US sites, FAANG companies but also smaller sites too, all flashing cookie/data protection type popups at me where they didn't previously. I've assumed that's because they need to comply with the CCPA which came into force last year, though it's totally a guess. I suppose their geoIP tracking may've just improved and spotted I'm in a GDPR country.

When does this type of legislation reach a point of critical mass where the UK is simply behind the curve and most companies just show the popup by default?

From a development perspective, having a whitelist or varying set of conditions per country adds complexity, I could very easily see a development decision being made to use GDPR as the common denominator and just code once for that, knowing that'll cover the company globally. Sure if your business relies on tracking and serving ads, then you may accept the additional complexity to behave different for different countries, but it still becomes a development decision that didn't have to be made before, and it's one with diminishing returns as legislation on privacy tightens.