Comment 34 for bug 1980018

The security theater argument is vacuous anyways, because you can already boot from a luks key stored on a removable media like a USB drive. Tpm is way more secure than that.

It sounds like they're going to do an implementation of it with a lot more security around it in a future Ubuntu release, but there's no real compelling security reason this couldn't be implemented as it is today, and improved later.