Why opensea (Wyvern) are using proxy registry?

From what I see when someone try to sell something on Opensea this is the process:

  1. The user creates a proxy registry for his token.
  2. The user approve the proxy registry to access his token.
  3. The user listing his item and sign a message to allow the buyer to buy later using that signed message.

Now my question is: Why do we neeed the proxy registry? What exactly it gives that cannot be done without it?

I have tried to read the Wyven whitepaper, source code, Opensea help center and all the docs, all the blogs posts published by both org's, and didn't find an answer.

You awesome! , I really want to know that now.