Fireflybob
And then at some units we get passed the QNH when we call for taxi as well
There's a very simple reason for this.
On the controllers flight strip (be it electronic or conventional) they have a box where they have to note down the QNH that you have read back. If the box is blank when you call for taxi, they will give you the QNH so that they can note in the box the QNH that you have read back. They can't just write in 1002 because you've copied XRAY, they need to hear the words ONE ZERO ZERO TWO.
Why did they wait till you were taxying?
1) they forget to write it in the box when you read back the QNH with the clearance,
2) they forgot to give you the QNH with the clearance,
3) they don't have electronic flight strips and the ground controller has a responsibility to check QNH and cannot reference the QNH that was read back on the delivery frequency possibly an hour earlier.
Either way, is it a hardship?
I also agree that the person noting down the ATIS (Captain or FO) could write it down incorrectly. 1002 instead of 1022 is a massive difference and yes you should notice that the airfield elevation doesn't match your altimeter when doing your instrument check but it's belts and braces and why do away with the braces for the time it takes to say ONE ZERO ONE ONE?
I personally don’t usually say the words QNH or Millibars I simply say I’ve copied XRAY ONE ZERO ONE SIX, it’s quick and ATC know I have the correct QNH.