From listening on my trusty hand held receiver I am very surprised at the amount of reading back by pilots of instructions that are not required by AIP to be read back. G'days, cheers, thanks, please, all these are superfluous yet are common on the air waves. These are only minor non-standards but other read backs are just nothing but lazy practices based on "when in doubt, read everything back and the bastards can't nail you".
Is the clarity of VHF transmissions in Australia so bad that reading back of practically everything is needed? What is good for ICAO is not necessarily good for Australia where the vast number of R/T transmissions are in Aussie accents.
Perhaps the number of excessive read backs could be reduced if ATC gave an instruction or clearance adding the words "Read Back" at the end of the message. No read back needed unless the controller asks for it. It would take a quantum change in radio procedure philosophy from ICAO recommended practices which are aimed primarily at the English second language (or third or fourth) operators.
After all, the last time I looked, the term "Read back" was still part of ICAO terminology. My bet is the steady increase over the years of additional read-backs published in AIP, is probably due more to arse-covering in the legal sense rather than a history of mis-understanding by pilots.