Source: https://www.niemanlab.org/2018/07/am-fm-radio-holds-strong-f...
https://nypost.com/2017/11/08/americans-check-their-phones-8...
Example: checking 100 phone notifications about spam email is probably less important to society than a radio alert about a tornado warning.
I'd expect people mostly listen to radio because they are bored while driving, which has about as much "importance".
Dead phones and offline towers are not unheard of in disaster situations.
For example: https://twitter.com/CarmenScurato/status/910957644256546817
I doubt it's either of those things. We can't begin to make quantitative comparisons with those bare facts. I just thought we could make a very simple qualitative deduction--that terrestrial radio is far more popular than many people believe.