I would say you are equally likely to catch someone jacking off through the webcam as to catch valuable information through the microphone. They are therefore equally lucrative
If I am in a conference room talking about strategy, an uncovered camera will just pick me up. The microphone will capture everyone’s conversation.
Beside I'm not sure a "jerking face" would be more than awkward if published. A reverse angle in which you could identify what was the video used for the jerking session would be way more compromising.
And in this regard poorly protected IOT surveillance cameras have way more evil potential that webcam in my opinion.
Also what are the chances that a microphone wouldn’t overhear something incriminating even if the camera were covered in your bedroom?
And I am really not trying to go down the road of wondering if you are doing something incriminating in your bedroom and your partner is being completely silent what that implies.....