[scriptedfate]

Antennas, broadly, need to be some fraction of the wavelength of the wavelength you're trying to capture. Think resonance as to why this is the case.

Since FM operates around 100 MHz, cellular around 1GHz, and Wifi from 2-5GHz, you'd need a pretty "flexible" antenna to talk them all at once. To say nothing of the capacitive footwork you'd need to undertake to adjust the electrical length properly to tune the sucker.

Couple this with how FM Radio is seen as niche for smartphones and it makes sense to have an external antenna requirement.

There is no requirement for the radio app to output to the headphones that are being plugged in for antenna reasons. The built-in app for my BlackBerry Z30 has no problems reassigning output to a speaker.