I've seen legal depts fight against this. They're worried the recording will capture some question or comment that could be evidence of discrimination. (e.g. someone asks "Did you have a good Christmas?" and is later accused of discriminating against non-Christians)

it's unnecessary to record the audio to solve the problem

Recording without consent is illegal in some states (CA, for example)

audio recording is. video is ok IIRC

And now you have a new problem that you've just signaled to all prospective employees that you don't trust them.