These figures are appaling and these "pilots" should be ashamed of themselves!!
Why? They don't do it deliberately.
I hear some appalling stuff on the radio almost every time I fly but I don't blame the pilots for this. They are the victims of a training apparatus which could have been written in WW2, and most of them fly so rarely they can probably barely remember which knob in the plane does what. A large majority are non-transponding (yet in most cases the aircraft types involved would not qualify for the standard anti-Mode-S outcry that the plane has no electrical system) which must make ATC tear their hair out at times. As well as making a RIS nearly worthless - if you can get it in the first place, that is.
However, I think it opens a wider debate about the quality of training or rather the required level of knowledge required to pass the PPL ground exams.
Why the ground exams in particular? I've done both the JAA PPL and the standalone (not piggyback) FAA PPL. 6 or 7 exams for the 1st, 1 exam for the 2nd. There is more really relevant practical stuff relevant to flying in the single FAA exam than in the multiple JAA ones put together.
Yet more rigorous ground exams are not the answer.