Because you don't pay that much for something to be durable if the durability will just be defeated by obsolescence. Whereas if you could upgrade it to later generation processors, clumsy people would save themselves a lot of trouble to buy the chassis once.
I guess we're talking from a completely different range within spectrum of laptop computing. Hinges, shells, flex cables, power ports, etc. all tend not last longer than hardware end of relevance for me unless it's one of rugged ones, but my use case is to throw into a bag and strategically yeet onto another luggage kinds.
