Cheap laptop I've bought in 2011 went through several upgrades: replaced ram doubling amount of GB. Replaced HDD with SSD, added HDD instead of DVD reader. Even replaced CPU to get more cores!
Nowadays I can only replace m.2 stick to get more storage. Everything is soldered.
Today there are also plenty of cheap models that support memory expansion and have an additional slot for an SSD. The only exception is the ability to replace the processor, which is extremely rare. So you should rather ask yourself why you, as a consumer, chose a non-upgradable model.
Compared with 8 bit home computers appliance nature, that wouldn't be a big problem if we had repair shops all over the place, which could nonetheless take over replacing/upgrading soldered items.
I do agree having back user upgradable ram, disk and GPUs on laptops would be much better alternatives.
It's not, you're just ignoring two obvious points:
1. a person with no laptop would prefer it
2. a repairable laptop can also have its parts upgraded, so a 20 year laptop could have 1-year old parts