I guess this depends a lot on the specifics of the job and place, but still I am not sure that parts upgrades on laptops are such a common thing for professional users. Rather, when computers are bought for business, then it is common in taxation law that their cost can be tax deducted over X years - so that is how long they will have to last, and lasting even longer is irrelevant. E.g. in my country X=3, so at my workplace (research institute) we get new machines every 3 years, and the old ones are dumped or handed to interns or whatever.
Don't get me wrong, on my private computers I value longevity and upgradability very much, and generally I am clearly for modular computers. I just think in the professional area the benefit of modularity is easier repairs rather than long-term upgrades. And many businesses will probably not even care about the repairs, they have some service contract and get a new machine if something breaks. In fact, the only problem I could see for totally soldered computers at my workplace is the fact that we are not to hand out hard drives/SSDs, and I'm not sure whether our disk shredder can take whole laptops.