There is an element of rods for our own backs here.
Standard procedure is to report ready for departure. Then at busier airfields, e.g. LGW as mentioned above, you are instructed to monitor, not contact, tower.
Hence unless some kind of 'be ready immediate' instruction is given, or 'are you ready immediate' question is asked, there is going to be the possibility that the aircraft is not ready. So what we see is this:
Due frequency workload, one piece of standard RT is removed ("Callsign, Ready for departure"). By so doing, situations are created that require the creation of additional routine calls by ATC.
Net result? more scope for errors, little if any change in RT workoad.
Obviously, anyone clued will keep tracks on the inbounds and inform tower that they are not ready as they are given their line up instruction, rather than waiting till on the runway. But even so, its likely to upset towers game plan.
Similarly, when checking in with tower from approach, I was trained to report my position, to improve everyones situational awareness. E.G. "Callsign, 6 dme" or somesuch. Now, we are routinely instructed to contact tower with callsign only, so when we check in aircraft at the holding point do not immediately know where we are unless ATC tell them. So...... ATC have to tell them.
So again, argueably we are not actually reducing total RT traffic, but just piling it up on the ATCO.
I don't really have a bone to pick about this, its no biggie, I'm just in contemplative mode.
CPB