radio reception inside a big box store is indeed limited, whereas cellular almost always works.
that means there won't be an issue with streaming audio, not that very many people listen to the radio inside a store. almost nobody, in fact.
you're making the opposite point you think you're making.
very rarely.
nothing is 100% guaranteed everywhere.
what you fail to understand is that the number of people for whom there is no cellular or wifi at all is much less than the number of people for whom there is no fm radio.
then streaming audio will work perfectly fine.
you're making the opposite point you think you're making.