As someone who has been dealing with exactly this issue with my new employer's enterprise ICT department, I have some insight to share.

When you have thousands and thousands of laptops that you need to manage, it becomes a burden for the in-house IT department, so they often farm it out to a Managed Service Provider (MSP). This is particularly common for organisations like schools and hospitals that often don't even have an in-house IT department. The MSP will install policies and management software on the laptops to ensure the OS is up to date, the antivirus is not disabled, the VPN is configured correctly, passwords are changed regularly, etc.

Yes of course there are linux-native solutions for each of these things, but the MSP doesn't support it, doesn't offer that service. To keep their service prices affordable for enterprise organisations, MSPs usually hire the lowest cost technicians and support staff. These poor underpaid staff probably have never even heard of Linux. The MSP can increase their marketable value by advertising the certifications they've attained. The certifications are provided by Microsoft and are related to Microsoft software and systems.

If you have a small fleet of devices and an in-house IT team that has a bunch of Linux enthusiasts, and a user base who drives demand, then it is possible to support Linux. But it requires a lot of effort and dedication. My old employer did that. They had a fleet of around 5,500 devices (a mix of desktops and laptops), mostly Windows, approx 500 of them were macbooks, and about 50 were Linux. Some of these were users who needed to use software that is available only on Linux, some were like me who are simply more productive and efficient using a linux-based OS. But maintaining, administering and supporting those 50 Linux devices took around 20% of the time of the IT department. That's massively disproportionate to the number of Linux users.

Not long after I left there, the new CTO put an end to that, they saw and easy cost saving by simply refusing to allow users to have any OS other than Windows.

Ease of management and surveillance (most such tools marketed at schools are Windows only), first class integration into active directory for user and computer account management, hardware agnostic (rules out macos), and it's already integrated into the IT team's systems and processes so switching would be a major effort.

This is a fairly naive take. It's this way because the infrastructure is built this way. If it was easy for an org to entirely switch to Linux, they would.