> Why is this sort of question always framed as […]
OP didn't frame it any way at all as far as I can tell, but either way it seems like an entirely reasonable question to ask of someone on a forum which is largely comprised of computer and programming enthusiasts who has not upgraded their daily driver for nearly a decade.
> as if spending money on the new shiny without any reason is normal or desirable?
Every single person who spends their money on "the new shiny" has a reason. You may not find the reason edifying, but that's irrelevant to your stated argument.
> Why would anyone waste their cash to replace something that works without having any compelling reason?
As you were doubtless aware when you specifically constructed a straw man argument predicated on an entirely false premise and laden with your own subjective judgements about "waste" and things that "work" and "compelling" reasons, nobody does this.
I suspect what you really mean is that you believe people upgrade their machines without what _you_ consider to be a good reason. You think people are too quick to upgrade when their machine isn't the very latest, or when it's got a dent, or when it's slowing down a little.
If you'd written what you really believe -- that people should not upgrade as rapidly as they do -- you'd probably have pulled on the thread for a further 0.02s and realised that everyone has different values and priorities, and you likely "waste money" in others' eyes across multiple line items of your annual budget. So it's terrific luck, really, that the internet's various competing interpretations of a "compelling reason" can't stop you from spending your money however you'd like.