There’s nothing baffling to it. Windows PCs are upgradable.
We're talking about enterprises here, not home tinkerers.
Enterprises buy whole computers and replace them every x years. They don't waste expensive IT employee time running around upgrading machines all the time.
The last time I worked for a company that did any repair of its computers was around 2005, when all ~500 Dells in the office had to have their defective motherboards replaced.