It's largely not about desktop. Linux is a dominant OS in servers, where customers want all the security features enabled and functioning flawlessly.
Eh nobody in the server world is using TPM, it's a feature build as a sort of EZ Mode endpoint protection. You use FDE and then store the encryption keys inside the TPM module and rely on the TPM security to protect them and if the user forgets, you can use the admin key to recover the device. The real way to do this is through something like Vera Crypt where you do FDE then use a passphrase. Of course users tend to forget those then expect the IT Department to all "Super TV Geek" and magically decrypt their device and recover the data.
Servers store everything on disk arrays and the hypervisor takes care of any volume encryption, if that's even wanted since walking out a datacenter with a disk array is rather ... difficult.
Furthermore TPM only protects the data from a casual thief, it doesn't do squat against a determined adversary as it's easily defeated through hardware bypass, or through the government agency just getting the decryption keys from the manufacturer.