>If you can read arbitrary process memory, you're probably also in a position to just dump out the passwords by pretending to be the user in question.

This is the load bearing argument and it is false.

There are plenty of circumstances were you can grab a piece of process memory but not all of it.

There are plenty more circumstances where you can grab process memory but not kernel memory.

There are plenty more (almost all) where you can dump kernel and process memory but you can't access the keys stored in the TPM module.

Leaving the door open for anyone with the smallest exploit is stupid and bad security.