Perhaps it is rooted in system admin's job security fears?
I see this kind of idea floated in various situations, and it always seems bizarre to me. As someone who has worked in quite a few IT roles in quite a few different companies, I don't think I've ever run into a sysadmin who was making things more difficult for the sake of job security.
I've seen sysadmins do counter-productive things out of pride and stubbornness, unwilling to entertain a new way of doing things. I've seen them continue to use ineffective solutions out of fear, believing that the alternatives are too difficult to learn, too difficult to implement and support. Speaking generally and anecdotally from my own experience, sysadmins will enthusiastically welcome anything that means less work for themselves.
And "If everyone used Linux, there would no doubt be less demand for cleaning up PCs"...? No. People make that mistake all the time. "The IT department is pushing back on our goal of moving all of our servers to the cloud. It must be because they know it will mean there won't be any more IT work to do maintaining the servers, and they'll be out of a job!" Or "The IT department doesn't want to migrate to an all-Mac environment. It must be because Macs 'just work' without any problems, and they'd then be out of a job!" Sorry, no. Unfortunately, there's nothing that will get we IT people out of our jobs.
Speaking for the sysadmins, we'd almost welcome the soul-crushing unemployment if it actually meant things would work properly. But no, really you're just changing the nature of the work we need to do. Instead of maintaining our own servers, we then have to figure out which cloud service will work for the business needs, work out an implementation, and then manage and troubleshoot the cloud service on an ongoing basis. Moving to Macs or Linux machines, it just means we now need to figure out how to replace all of the Windows-only business-critical applications that your business is running, and then come up with a scheme to protect and manage all of those Mac/Linux workstations. Believe it or not, a Windows DC with Group Policies is a pretty effective way of managing a lot of desktops/laptops.
So either way it's work, and it'll require someone with expertise. And no matter what, it's not going to quite work properly. We're usually just looking for the path of least resistance.