Because PC gamers often buy desktops. And console gamers buy consoles while handheld gamers buy handhelds and smartphone gamers...
Then there are other kinds of laptop users... the various Macbook users from the lightweight travel Air to the beefy desktop replacement 16" Macbook Pro, and the Windows business laptop users, and the Linux laptop users.
(I think we'd all do well to remember the variety in computers and computer users...)
So yeah, I've rarely bought anything but a gaming laptop that could easily be upgraded via RAM or SSD, and when I've bought non-upgradeable laptops (a tiny Asus 2-in-1 touchscreen) I found it just wasn't for me and I ended up selling it.
My favorite gaming laptops... Lenovo Legion 5 Pro, Acer Nitro 16. My spouse uses a Legion 5 Pro. My sister uses my 5+ year old Legion 5. They've all been a combination of good or great screen, great keyboard, good hardware, pretty quiet except when cranking up for demanding games, and so far all have been reliable, upgradeable, etc. We don't tend to use them on battery, but I've found that they tend to do 4-5 hours easily for basic usage. I wouldn't expect them to do well at all when pulling 100+ W for gaming. (My sister had an older Nitro and the quality was lacking, but I've been impressed by my 2023 model.)