I have noticed on flight deck famil flights that it is relatively easy to keep a picture of what is going on in familiar sectors, I know where and when who calls, and can follow what is happening from the chatter. I also noticed the crew on each occasion were completely oblivious of this, and didn't even appear to be listening when their c/s wasn't mentioned.
A crew I flew into Adelaide with once were mystified by getting a speed reduction in the cruise. I pointed out the 4 aircraft that were transferred to our current frequency before us were probably in the sequence ahead of us, including the 747 that was track-shortened around us. They looked at the TCAS, saw nothing and said I was talking ****e, until I pointed out the 747 in our 2 o'clock!
The corollary is I'm completely adrift in a busy unfamiliar sector.
I suspect some of us on the ground greatly overestimate the usefullness or practicality of aircrew getting much of a picture from the 'party line'.