Comment by sern

I think a better reason than "not wanting to play fair" is that the Apple implementation preserves the correct operation of the mic even while the remote is being pressed. Apple does it using a custom chip within the remote that superimposes an ultrasonic tone on the mic signal which can be cleanly filtered out, whereas resistor-based signalling works by shorting the mic signal to ground which either mutes or attenuates the mic (depending on the specific button and resistance involved).