It's not actually used for DRM, that's part of Intel ME and why AMD PSP is closed source. Both of those are involved in setting up "protected media path" which is all about setting up encrypted channel between display and media player to prevent sniffing.

TPM could be used for DRM in the sense that DRM software could refuse to run on system that isn't approved, but it's not going to stop you from enjoying a DRM free system - in fact it can help by explicitly supporting clearing of TPM state by owner.