Capt,
I agree with your post entirely, but there is a catch in this brave new (shrinking) world of international cadet programmes.
e.g. "Alpha Bravo Charle, report established with DME and altitude passing", only requires a response of "Alpha Bravo Charle"
This callsign only approach does not allow anybody to know that the student pilot has actually understood the request. Now, there is the argument that if they do not understand then they have no right to be there, (and before you all start throwing stones at me) I fully agree.
The fact is though, they are there, they dont always understand, and they will take up more airways time.
As frustrating as I find it, I personaly would prefer to know that they understood the call now, as oppose to latter, when it could be more critical (separation requirement). And lets face it, there would not be one single person here who as never spent longer on a call then required at some point.