These companies learned their lesson with the open BIOS of pc's preventing them from really controlling DRM.
Android, not having a standardized BIOS, really gives them the opportunity to provide devices they can fully control.
If you can't unlock boot, you can't root, so you can't fully control the device.
That's the long-term goal: get people used to devices they don't actually control.
Lots of people already don't know the massive difference between using a full desktop app and a limited mobile app, many actually prefer the mobile because it's simpler! (I admit I do too, for certain use cases and maybe day-to-day use, but not for all use).
And then all the people who argue against having root access on your own device. 🤦♂️
There are good arguments for much of what Google does to improve Android security, it's just very frustrating to know their real agenda is to lock us out.
Fortunately, businesses will always need MDM (Mobile Device Management), which will require root access in some fashion, and there are already Open Source/low cost/free versions of MDM out there, and plenty of smart devs always working on root, like Magisk by topjohnwu and the new KernelSU by tiann (which gets root at the kernel level!)