My guess is that valve clearances become more important at higher revs. I suspect 
that your Audi, or those inter galactic turbo diesels, don't rev to 13,000 rpm.
A decent car will spend most of it's life at 2 to 2.5k rpm where a bike such as a K1300S or my H2 SX will spend most of it's life 5 - 7k rpm that means the valves have opened/closed 3 times as often for the same mileage but still have to be light enough open and close 100 times every second when running at 12,000 rpm.
No, you are quite correct David. Even my breathed on, 2 litre dohc (chain driven, note) turbo slightly loopy nutter bastard (as opposed to the absolutely bonkers mad version RS3) is only burbling along at 3,000 at the legal limit of 81'ish. You'd have to be on a track or a very deserted road with a death wish to be troubling the higher reaches of the rev band. There are some lovely open twisties around me and at the witching hour, floating round at the same speed is a calm, quiet rush with absolutely no need to change gear apart from the odd overtake.
So, yes. Whereas my A6 3 litre turbo diesel was wafting along under 2,000 for most of its life, even at the same speeds, my petrol A3 is doing 50% more rpm for most of its life.
7,000 is about the limit for hydraulic lifters, so meh!
