By the time I’ve ever wanted to upgrade a Windows or Linux PC, a new CPU probably isn’t going to fit into the same socket as the one I had so now I need a new motherboard too. I probably want a new GPU if it was a gaming PC and if it wasn’t I would be using an integrated GPU anyway.
I think the only thing I’ve ever kept from an “upgrade” was my case and some memory sticks. But I probably would have been better off—both in time and money—just selling the damn thing as a whole and buying an entirely new set of components.
TL;DR, year-over-year bumps just aren’t worth the price of upgrades, but by the time it is worth doing you probably want to upgrade so many parts there’s little left to keep. YMMV.