Because Bluetooth sucks. It's a shame it's the industry standard.
Bluetooth support is still spotty on Linux, which to me is continued evidence that the stack is complicated and bug-ridden.
Even for my high-end BT devices, there are still lots of problems. In addition to the problems listed elsewhere in this thread, I particularly have problems with:
* Easy, reliable switching between connected devices. * Reliably connecting when a device is turned on. * Audio delays on the order of 200ms.
I stick with wireless almost exclusively, because I hate the wire, but I switch to wired for gaming because a 200ms audio lag for a real-time game is unplayable. 200ms is obvious even just watching someone speak in a video.