That would be as good as full-disk encryption, but it is possible and useful to do better than that with a TPM. With physical access to a running machine, it is

That would be as good as full-disk encryption, but it is possible and useful to do better than that with a TPM. With physical access to a running machine, it is possible to physically extract data from RAM. Law enforcement agencies even have hotplug devices that let them switch a running computer to battery power so they can seize it while keeping it on and do this.