TD...i...don't get it

[BW2309]

OK, so not really a classic car issue as the TDi craze is on modern Audi's but I was wondering something. While sat in the "library" at home this eveing I was reading of Audi's success in racing with the TDi's and how this technology has changed the face LeMans.
Now, after being privaliged to own an '04 Audi A8 V8 TDi I can vouch for the performance of the modern TDi's. After the success in LeMans and the SEATs in racing also, how come Audi aren't playing on this by making particualrly sporty diesel road cars? ALL S and RS models are still very much petrol powered...... Does this mean that despite the improved and frankly remarkable performance of TDi's we are just not ready for diesel Performance models?? Is it worth all the expence in devolping racing diesels to not bother with sports diesel road cars???

Your thoughts please cos it's buggin me!!