It's not to trim the BOM, it's because electric vehicles emit copious amounts of interference. It is easier to drop AM radio than suppress the RFI.

https://www.nytimes.com/2022/12/10/business/media/am-radio-c...

Technical point, you generally would not be able to recover an AM broadcast signal from a cellular baseband. You might be able to get it from a direct sampling receiver (some RTL-SDRs can do this), but it implies additional band filters and of course an antenna.