Tons of PCs still ship with 8GB RAM as well. I don’t know how much it hurts margins to sell 16GB to people who would be happy with 8.
However, I suspect that a large portion of PCs are used as-is and are replaced rather than upgraded, much like phones or tablets.
It's worth noting that Steve Jobs was originally against RAM and other upgrades for the Macintosh. It was supposed to be an appliance like a toaster, and (most) toasters are non-upgradable. He also didn't want it to have a fan - making it more like a toaster or a MacBook Air.
So I really don’t care what anyone says, there is definitely something special about Apple Silicon re. RAM usage. Maybe it’s just swapping really fast. Doesn’t matter, it works.