Why do you need headphones for radio?
Marconi sent the first radio message across the Atlantic Ocean in 1901 December and he was also awarded Nobel prize for his invention. Fine! That's a great piece of information but Why Can’t You Use FM Radio Without Headphones?.The Smartphones do not currently have a built-in antenna. So we require a headphone which must remain plugged in to receive FM Streaming.
How do headphones work as an Antenna?
An antenna is a metallic structure that captures and/or transmits radio electromagnetic waves. Headphones are cylindrical in shape, with a grooved tip to retain it.. It works just like an antenna by capturing up the radio wave and providing it to a tuner.
FM radio works in the range of 88 to 108 MHz. Antenna length is proportional to the wavelength of reception. Headphones are of that length mostly and thus can be used as an alternative to an inbuilt antennae.
Earphones are included in most mobile phone purchases with the box. Even if the Smartphones were included with an inbuilt antenna, the user will be using headphones mostly. In such scenario either one of the two antennas inbuilt or external headphone antenna will be serving the exact same work wasting the inbuilt antenna's worth.
Including an Inbuilt radio antennae will make the Smartphone weigh by few more grams and would also increase the thickness of the phone, not a desirable attribute for marketing.
A simple metal wire can do the trick with which you can listen to the radio! Therefore, in reality, you don’t necessarily need the headphones to play FM radio on your cell phones but you need an antenna.