That's simply because these remote controls are transmit-only, fire-and-forget devices which spew out a pseudo-random code to the receiver without being able to listen to any response. This is also why you should not click the button on the remote too often (as in 'more than 255 times') when not in range of the car as that gets the transmitter (key) and receiver (car) pseudo-random generators out of sync - the receiver accepts a sliding window of 256 random codes as valid. There might be different implementations of this feature using key fobs but this describes the majority of them.