As jpiniero said, you don't want to be responsible for supporting it especially not within a big company. Just having to RMA broken parts makes me shudder if you have to go through SAP or the likes. Simply a road you don't want to take if you mind your own sanity.
It depends on technician bandwidth. For example I work for 3000+ employee company but am only responsible for my ~100 employee satellite. I am the only real technician at this location responsible for purchasing, supporting, and repairing any of our employee computers. I'd love to tell our engineers to get threadripper or push for 4800h workstation laptops (well I would be less likely on that) and building stuff is my favorite part of my personal computing hobby. But I can not and will not ever suggest that they let me build systems for them. But I could see the main branch doing it for their employees. An example, every laptop I purchase I purchase with a 5 year warranty, why, mostly because if it goes down I need the manufacturer in next day to resolve the issue for as long as we might need them. I can't be out of commission for a whole day trouble shooting an issue with a single system. My parent company on the other hand by laptops in such bulk that they don't purchase extended warranties on them, to them if lets say 5 systems act up in a month, loading a different system and trashing any system not fixed by a reload is cheaper than purchasing the warranty on the 50-100 systems they might purchase a month or quarter. They have 50-60 techs, each tend to have different specific jobs (to much job siloing going on) but could probably get away with having a tech just working on TR systems and between engineer workflow improvements and the labor for some pretty low level tech would make it worth it.
But that probably even then is a mid level business aspect. They could do it because the amount of services in general requires a decent amount of trained IT guys in specialized tools and large enough to need a decent helpdesk. But you get to much larger and the IT size does another shrink as the rest of the business grows much faster then IT. So you get to a point that between the stretched thin, the amount of workstations you would need, and so on, it becomes too cumbersome again.