It is possible to have an AM radio that's not inside a car! Many homes have portable radios that are battery operated. Especially in areas that are prone to very severe weather.
The problem is there are parts of the US where cell signals and FM cannot reach but AM comes through just fine. Particularly mountainous regions, where weather and safety reports are important. Telling people driving around these areas to keep a second radio running in their car seems kind of stupid when the functionality can be included in the head unit for pennies.
Preserving AM radio is important for a few reasons that go beyond cars. AM broadcasts have exceptionally long range with relatively little power. Transmitters and recievers are among the easiest circuits to build completely from scratch, as there is no arcane or proprietary knowledge needed to decode the signal. For these reasons, maintaining AM radio infrastructure is an important insurance policy in case of natural disasters or other major public safety events, even if it is something 99.99% of people will not interact with on a daily basis.
Preserving AM radio is important for a few reasons that go beyond cars. AM broadcasts have exceptionally long range with relatively little power. Transmitters and recievers are among the easiest circuits to build completely from scratch, as there is no arcane or proprietary knowledge needed to decode the signal. For these reasons, maintaining AM radio infrastructure is an important insurance policy in case of natural disasters or other major public safety events, even if it is something 99.99% of people will not interact with on a daily basis.