Its kinda useful for devices where userland is also protected against exfil, like a kiosk or windows lock screen.

If the bios is hardened, secure boot on, bitlocker on, and windows is locked with a password, you can't simply take the disk out and manipulate it cause bitlocker with TPM means only that specific hardware profile will decrypt the disk automatically.

You can't get to explorer cause the system is locked with windows auth, and you can't reset the PW cause bitlocker is on, and you cant remove the disk cause the TPM protects against that with bitlocker.

Its really not perfect, and I'm not advocating for it, but its a decent protection in systems where adding another pin/password isn't practical.

Even Microsoft recommends at least also using a pin with bitlocker.

I assume they think the Windows login password will keep them safe. I don't know. But many corporate computers (several I've been forced to use) do use Bitlocker without a password.