My take on in car 'yapping' is that it is track dependent. Some tracks, you simply don't have the time to talk about each turn. There is simply too much happening. Other tracks, there's tons of times between the turns.
Then again, the driver has to be receptive to this 'talking' as well and it's hard at times to listen, comprehend, act while they are also driving. Some people will tune out what the instructor is saying.