If the drone is registered in your name, people will be more careful to make sure they don't break any laws. Some of the same reasons we register cars and have license plates. People tend to act shitty when they know they won't be held accountable.

It lets you know who's playing in the sandbox, to extend the analogy. You can then use that to require training or stay in touch regarding changes to restricted airspace or whatever.

Now that I think about it it does let them take preliminary action before something happens and talk to the owner. So it's not as bad as I thought.

In and of it self nothing. Though I have to say I have never registered for anything that didn't include receiving a set of rules. I would be really surprised if registering didn't get you a pamphlet on how not to get arrested while flying a drone.

You're exactly right.