This is a very interesting insight. The vast majority of traditional unix security mitigations are about securing a multi-user system from malicious users. However a lot of the most frightening threat models now are about using data from a single-user system to hijack session tokens or other secrets and thereby compromise external systems that it has some sort of trust relationship with. That's why you see spearphishing attacks that compromise the clipboard - they are hoping that a useful secret gets copied from a password manager or similar. You don't need to elevate priviledge on the local machine if all the secrets are owned by the user you have compromised, and all these secrets are very small numbers of bytes because they are designed to go into a challenge response type flow.