Bugs and annoyances which not everyone is having. Stripping out functionality to crush bugs is like removing your stomach to get rid of a stomach ache.
There are cases and classes of hardware where Bluetooth is not ideal and 2.4GHz proprietary standards are used (low latency audio, gaming mice, concert/conference audio. etc.) but those devices already exist on said proprietary standard instead of Bluetooth since they're usually not meant to be paired with changing hosts/clients all the time like most bluetooth devices, so what's your point? Do you want proprietary dongles to ship with every pair of earphones?
2.4GHz proprietary standards are no magic silver bullet either. Sure, compared to Bluetooth they can have the advantage of latency and bandwidth depending on how you implement said custom protocol in firmware, but it's ultimately the same damn overcrowded ISM band shared with the billions of devices everyone has everywhere (Bluetooth phones, smartwatches, headphones, cars, IoT devices, security systems, and, the 400 pound gorilla in the room, motha-friggin-Wi-Fi) . So due to pollution on the 2.4GHz spectrum you'll end up with potentially similar issues like Bluetooth devices except now you have a proprietary standard to deal with.