Because the price tag is quite high to get as much storage as you would 15 years ago for about the same money.

I agree that many people use them as glorified internet machines but even then when they occasionally decide to back up some photos or edit a few videos the 256GB non-upgradable storage quickly becomes a limitation.

Price matters. 256GB is fine on a $500 web browsing laptop, but on a $1000+ one it's just a bad deal in 2025, even ignoring the fact that you cannot upgrade it later (it's soldered in place).