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.

There’s an accounting factor too. Businesses depreciate equipment as SOP. The laptops have already been written off by the time they need upgrading.