Why do they always use border collies for commercials?

When you look at any TV commercial with dogs, the dog almost always happens to be a border collie. We know that BC's are smart, but are there other particular reasons that they appear on commercials? Other dogs breeds are capable of doing it too. Even in commercials when the dog doesn't do anything, where they require no particular training for it, they still use BCs. Is it becuase of their appearance? What do you think?