Unfortunately folks I can attest that after almost 30 years in aviation I have witnessed the gradual but continual demise of good R/T phraseology. Once upon a time people used to think that it was a sign of our professionalism to use a frequency with the correct and concise phrases as described in AIP.
The impact of this loss is a greater propensity to misunderstand or misinterpret calls made by ATC or other aircraft thereby reducing safety. Further, the busier it gets on the frequency the more important it becomes to ensure you only give the required readback otherwise frequency congestion can quickly occur with some dire consequences.
The solution lies with Instructors at flying schools knowing the correct phraseologies and teaching them and Check Officers enforcing professional R/T. Listen to the R/T at any GAAP aerodrome and you will find that a lot of Instructors (including CFI's) do not use the correct phraseology in the circuit and so the student learn's these bad habits. Hence the demise in R/T standards.
May I suggest useful analogy? Imagine that a readback is like a receipt to a financial transaction. ATC issues an instruction as per AIP and you respond with the correct readback as a receipt to the verbal transaction. Your correct readback confirms to the ATC that you have heard and understood the instruction and will comply. Also when ATC issues an instruction to another aircraft wait until that aircraft responds before jumping in with your call.
It isn't that hard is it?