I had two phones being capable of listening to VHF FM radio (in Germany about 90 to 104 MHz). However when turning on flight mode, the radio receiver is also disabled, and I wonder why: Listening to radio does not transmit any electromagnetic waves (more than when playing some game I guess). I thought it would be some fun listening to the different radio stations while passing countries from above.
All broadcast-band radio receivers contain local oscillators which are used in their intermediate frequency (IF) circuits to downconvert the (higher) frequencies they receive. These IF circuits are prohibited by law from radiating more than very small amounts of radio frequency power while operating, but to prevent any possible chance of having the airplane's navigation receivers pick up interference from portable radios, they have to be shut off during flight.
This is a minor problem today, but old-school shipboard radio receivers during WWII were supposedly capable of radiating enough power off their IF stages that submarines could tune in on them and use them as homing beacons to track convoys and then sink them.
I thought there were some existing questions on this, but I didn't find a good match.
Listening to radio does not transmit any electromagnetic waves (more than when playing some game I guess).
That's not correct. Although the device is intended to be a receiver, the antenna and circuitry can end up leaking power on or near the received bands. For a well-designed, healthy unit, this should be minimal. But it's much easier for such transmissions to come from a receiver than from a game unit that has no antenna and no tuning circuitry.
I remember all the US airlines I flew on in the '90s explicitly prohibited operation of radio receivers during any phase of the flight, not just takeoff and landing. I haven't surveyed, but I think many more these days allow AM/FM receiver operation. I have no idea if this is because radios are less likely to cause interference, airplanes are less susceptible to such interference, or folks bringing radios on has dropped to levels that it's not worth mentioning. But United at least still appears to have them on their "do not use" list. https://www.united.com/ual/en/us/fly/travel/inflight/devices.html
So I'd say that due to the history, it makes sense that a device with "airplane mode" would disable any radio-band receiver circuitry by default.