As Apple Explained … well, explains, in an enlightening 2 minute video, iPhones were actually included FM tuners prior to the iPhone 7. At the time, Apple sourced their wireless/Bluetooth chipset from Broadcom. At the time, Broadcom included a radio tuner. It fell to Apple to add a simple circuitry upgrade that would have made the tuner functional on iOS.
This, they did not do. Per Apple Explained, the decision not to include a radio tuner app in earlier iPhones and to nix the radio transmitter entirely in later builds had less to do with engineering than, for lack of a better word, vibes. Terrestrial radio is old technology: local, range-limited, with varying degrees of quality control. That’s not the Apple offer. Apple works hard to deliver a smooth, seamless, futuristic user experience with minimal customer intervention and maximum stability across models and borders. Radio couldn’t live up to that, so it had no place on iOS.