CodexAG An attacker able to compromise your device gets all your data including your pictures/videos, documents, login sessions, passwords, contacts, encryption keys and everything else on your device. They can record and see everything done with the device. Kill switches don't stop any of that and don't stop them recording via the microphone when the user has it enabled to make calls, record videos, etc. or simply if they haven't turned it off. A kill switch for a microphone has an extremely narrow use case. To work properly, it has to disable access to other sensors usable as microphones. Existing implementations of this are largely incorrect and don't stop audio recording.
Camera kill switch has the alternative of shutters or other ways of blocking the cameras instead.
Kill switches for radios largely lack a purpose and are a solution looking for a problem. The purported purpose of these features doesn't make sense and goes against the basic logic of how security works.
Having a secure device preventing an attacker from taking it over is certainly far better than an attacker getting absolutely everything from your device and having full control of it, except that they can't use the microphone or camera if you have them disabled, so instead they can record low quality audio via accelerometer/microphone still able to decipher speech and can wait until you turn it on for any calls, video recording, etc. They still get everything else even if you always leave it off.
We would include a properly working audio recording kill switch on a device where we got to add a bunch of features we wanted. It would be a small frill providing a last line of defense when the device has nearly completely failed the user and gotten deeply compromised by an attacker, not a major feature with a lot of value.