Why does avr-gcc bother to save the register state when calling main()?

Question

The main() function in an avr-gcc program saves the register state on the stack, but when the runtime calls it I understand on a microcontroller there isn't anything to return to. Is this a waste of RAM? How can this state saving be prevented?

Answer 1

How can the compiler be sure that you aren't going to recursively call main()?