Why is it still not compulsory for all assessments to be audio recorded ?

Statisically If thousands of claimants all say the HP's written reports state the complete opposite of what a claim form and medical evidence state, Why would all these claimants really say they can do this and that when the above evidence states they cannot? It would help stop all the lies, and the HP could replay the audio to actually get a detailed listen to what was actually said by the claimants. It seems like a loophole has been exploited by the assessment provider, and the DWP has not done anything about it. You'd understand if 50 or so out of a thousand claims were written wrong because of non-suspicious circumstances, but there are too many. The recordings would be the sole witness to what was actually said and shut down the he said, she said (uncountable) conflicting reports from two parties on the issue.