I think they want you to only use Windows and pay for cloud storage.
By enforcing BitLocker and Secure Boot, they are trying to eliminate dual-booting (you don’t need to dual-boot Windows/Linux anyway, as you can just use WSL2 /s).
By enforcing disk encryption, in general, they try to force the use of cloud storage, by making data recovery nearly impossible. Most people are probably too lazy to buy external storage, and manually copy their files over.
This guarantees 2 money streams. One from Windows’s tracking/advertising and the other from OneDrive subscriptions.
My parents wouldn’t even notice that their computer decided to encrypt their files. And they will blame the service guy for not being able to recover their photos, in case of hardware failure.