IIRC, you have admin priviledges but you don't automatically have access to everything. To do certain things (at least on the command line), you have to sudo. It'll prompt you for your password (note - YOUR password. Even if root is enabled, sudo goes for the non-root admin's password) and then execute the command.
It's probably not quite as safe from a trash-your-system standpoint as the traditional Unix/Linux separation of powers, but at least you've got to consciously assume the SU identity to do some of the more critical things.