Bongo. It used to be that when phones had the 3.5mm jack, many included the FM module because it was cheap and easy. But with the disappearing of the jack and the headphone wire with it, there's no viable way to receive that FM signal. Most OTA analog wireless signals need a wire to propagate along in order to (for lack of a better term) collect enough of the signal to reproduce. It's the same reason old analog cell phones had the antenna and extending it while wandering around or climbing up on something helped the call come in clearer. Digital signals don't have that same issue, the signal is either on or off.

That is precisely the reason.