Though I don't doubt there's a fair chunk of forgotten/ can't be bothered etc, some places make the process incredibly difficult, or flat out refuse, or accept the new address and don't actually change it on their internal system.

Seven attempts to change my address with the GP. Seven times they said, "yes that's all sorted", then sent things to my old address anyway. (I did have a postal redirect set up, so was still receiving things).

When they send the "is this correct" for the electoral register, they (the council, I guess?) will re-add my partner's brother, who previously lived with us in a different flat, but has never lived in this house. They will also remove him from his actual address. We'll fix it again, and they'll do the same next time.

A power company had my name wrong for 10 years. They wouldn't change it, unless I could supply ID for the badly misspelt name on the account i.e. "We're sorry, Mr John Smith, but we're going to need permission from Mr John Smoht to change the name. If you can send us a copy of Mr Smoht's passport...".

Other's I remember less specifically, "Send us your change of address request by fax" and "You have to come to this building to change it, but only this member of staff can do it and they're off on sick".

If people can't be arsed to take five minutes out of their day to change a small thing, then that's their problem.

Not sure how it's the government's problem, given that we're bombarded with "register to vote" adverts around election time. They can't register for you.