My mum is in her late 70's and has a $6k hearing aid that is tuned on a PC. The FDA don't want to prevent people tuning their hearing aid with their mobile phone, they want to ensure they can't accidentally blast their brains out with a 130db screech in the pitch of a 6yo girl. They will also want to look at the hearing aid to ensure it can't be used as an audio torture device in the first place.
It's well known that principles are expensive. The majority of the $6k for the device and software represents the cost compliance with the "first do no harm" principle that has been central to western medical practice for over 2000yrs, money well spent IMHO.
Pre-emptive "free market" retort: Hearing aids and the software that interacts with them are tested, certified, and sold as a standalone "system". Everyone is "free" to play in that "market", although individuals and groups have varying degrees of influence on how the market works, they are not "free" to dictate the rules of trade that constitute the market itself, that's the role of government.