Most smartphones come with a built-in FM radio chipset which is disabled by the phone manufacturer. Apple, Samsung are just a couple of companies who disable the chip. Motorola & HTC and Motorola chips are reported to have enabled their chipsets.
During a local/national emergency where there may be no Internet or cell service, FM radio could be a critical and vital resource for information. The Federal Emergency Broadcast System broadcasts on FM stations, who are mandated to periodically test the EBS, and the ability to receive these signals in times of need should be enabled; either by default, or by user preference.
If there is no power grid due to a local/national incident, FM radio could be the only lifeline a citizen possesses.