Why? AWS manages to do it (https://aws.amazon.com/ec2/instance-types/mac/). Smaller companies too - https://macstadium.com

Having used both professionally, once you understand how to drive Apple's MDM, Mac OS is as easy to sysadmin as Linux. I'll grant you it's a steep learning curve, but so is Linux/BSD if you're coming at it fresh.

In certain ways it's easier - if you buy a device through Apple Business you can have it so that you (or someone working in a remote location) can take it out of the shrink wrap, connect it to the internet, and get a configured and managed device automatically. No PXE boot, no disk imaging, no having it shipped to you to configure and ship out again. If you've done it properly the user can't interrupt/corrupt the process.

The only thing they're really missing is an iLo, I can imagine how AWS solved that, but I'd love to know.

Where the in the world are you working where MDM is the limiting factor on Linux deployments? North Korea?

Macs are a minority in the datacenter even compared to Windows server. The concept of a datacenter Mac would disappear completely if Apple let free OSes sign macOS/iOS apps.