Purpose of Peerages

I've been in the game a long time, and I wanted to get other perspectives on this: What is the value in Peerage(s)? What purpose do they serve to the Peers themselves?

I ask this because I've seen a lot of great and wonderful Peers, and I've seen a lot of terrible Peers, and I want to understand what Peers get out of their Peerage, and what non-Peers perceive about Peers.

Is there value in pursuing a Peerage, outside of the beneficial experiences and mentorship one gets along the Path? If a Peerage is a demonstration of ability, how does it differ from a GoA, outside of the politics involved?