Why do you people hate having an extra feature? What would be the matter activating the chip and requiring users to plug in headphones or a charging cable as an antenna if they want or need to use FM. The difference between having an extra device at home for disasters is that you most likely have your phone at hand most of the time and that you might have no more home to get your device from after a disaster.
Thing with FM is that (as other users already pointed out) it doesn't overload (ever been at a large accumulation of people like a festival, city event, sports match? Imagine being in a disaster zone with everyone trying to get internet connection) and that the frequencies get higher reach and are easier to deploy in temporary setups so there's more chance of you being able to receive radio or emergency services.
Also, DAB+ is a digital signal so it's either on or off and not just some reception which the guy from Switzerland should know from driving through tunnels so that again is fallible. Also, cars aren't build with DAB+ receivers, that still is a $500 extra feature that only rarely gets build into most cars apart from the richest markets.
Last but not least, I've never been to the US so I can't tell how ****** your radio stations are but FM radio still is a major thing across Europe with a large variety of quality stations. Most users listen to it while driving their cars, many have radios playing at home, in their kitchen or at work. At least here, FM isn't dead and that in parts is due to the technology difference of analog signals vs. digital and their issues. Also, this poses a good backup option for if digital systems really are down or reception is bad for some reason.