Aside: I may be able to switch in a couple months... I'm literally working on isolating a windows tether in the primary app I'm working on into an isolated service. After that, it'll be separated enough that I won't have to support it. We also have some other projects that are k8s/docker/linux as the target, and some of the contractors are using macs. So may be able to make a case for a switch.
edit: My experience (elearning, banking, govt) has been no companies supporting desktop users on linux. Though some VM deskop use for software on non-windows servers.
So, the monoculture was there when the new projects started.. the majority of developers and staff are from/in a windows and microsoft centric world view.
Moving stuff away from that has been very hard, and something I've worked hard to make an effort on... I'm not sure where your dogma comes from, but Linux 20 years ago was not what it's been for the last decade even.
It could partially be to maintaining a desktop OS. GPO / SCCM helps manage computers with scale. I'm sure there are Linux tools, but suddenly you have 2x more work to secure, patch and keep up with the best practices for your workstations. Moreover GPO and SCCM is IT friendly way of managing computers.