As I've said before, every cubic millimeter of volume in a modern smartphone is expensive... it is precious.
Even if that functionality is available on one of the multiprotocol wireless chips, adding even a tiny amount of support circuitry to enable may not be a wise move from a product design point of view.
In the USA, an FM receiver isn't going to sell phones. VR, better cameras, longer battery life, etc. sell phones.
Exactly, and it's not like forcing that function to be enabled in the chipset is going to magically install an antenna/amp into a device that doesn't have it.
Apple has already done away with the headphone jack, and re-enabling use of the headphones would probably mean having to add a receiver to the tiny circuitry in the plug that houses the DAC. That sounds like a lot of work for a niche feature, and it's not going to help users of wireless headphones either.
Every cubic millimeter is precious... because we make our phones so thin that you end up buying a protective case to add some heft since it's so thin it wants to slip out of your fingers. Then you also buy a portable battery to top off when that super thin battery runs dry in the early evening.
Would it be really so bad if someone made a smartphone that was ~2x as thick as an iPhone, with added battery life and usability?
Unfortunately, it's in these companies best interest to push a new phone every year, regardless of if the new features justify the added cost... or are even features.
All you need to make FM radio to work is to just connect ground of headphones to a pin, but it is connected to pin anyway, so no extra hardware is required.
Even if that functionality is available on one of the multiprotocol wireless chips, adding even a tiny amount of support circuitry to enable may not be a wise move from a product design point of view.
In the USA, an FM receiver isn't going to sell phones. VR, better cameras, longer battery life, etc. sell phones.