As many have stated before the tower need to check you have the correct QNH it doesn't take long and it's safety critical. LL check once and that's all that's required.
We need to hear the QNH because it's the rules, simple as that. You want it changed, contact the CAA.
Regarding unneccesary RT it does work the other way. I hail from the LL radar environment and on first contact a/c should pass cleared level, a/c type (yes this is important as I've lost count of the number of incorrectly filed plans, including a few vortex changes!) and ATIS letter.
Now it has become common practice recently for some crews to also include the QNH on first contact with LL director. Why? It doesn't bother me, but 99.99% of the time the a/c is direct to the holding point cleared to a flight level not an altitude. I'll inform the a/c of the QNH when I descend it to an altitude there is no reason for the crew to tell me what it is when they're still at flight levels. Another midly irritating thing is when an a/c is cleared to succesively lower altitudes and continues to read the QNH back with every successive clearance, even though they've read it back correctly once already.
I fear unnecessary R/T loading is a crime committed on both sides of the radio. We need to minimise it without removing the safety nets.