I'm wondering why rails automatically generates 2 separate actions "new" and "create"

I seem to remember reading something about this on this forum, but I can't seem to find it. Anyway, why not use 1 action "new" and then have different logic depending on if the request is GET or POST. Is there any advantage to splitting it up like this? Is there a disadvantage to having it in 1 action?

One disadvantage I see is when you have select lists. If I want to populate my view with a select list, and if I'm pulling from the db in the controller, then I have to have code pulling the list from the database in both actions, as opposed to one.

Anyway, I'm interested to hear what others are doing.