You have to constantly have an eye on your rev counter, if you don't you're either going to damage the engine or not go anywhere in a hurry. When you're truly driving fast and near your limit and having to concentrate on other things, you do not have time to listen to the engine revs, there are far more important things to do, like listening to your tyres and for any mechanically worrying noises.
What possible logic are you using to come to that conclusion? I don't see how using a vehicle for a use it wasn't intended for is chavvish behaviour, presumably production based competition cars, ambulances and hearses all qualify as being chavvy in your book then?
Clearly you have never been on a track then...
I highly doubt they can hear much of the engine at all, as is typically the case in mid engined race cars, the chance of being able to judge the revs of a very fast revving engine like that even to the nearest 1000rpm whilst being thrown about at 4G with a whole manner of other noise is very low.
About the only form of competition car that don't need a rev counter are those that only use one gear, in other words some oval specials and karts, a lot of them still have a rev counter though because the result of getting gearing wrong either means throwing away a lot of time or money.