Ah, but the SC and IS's are. Both of them have raced on the JGTC and Australian Grand National Circuits for a couple of years. The SCs are heavy, true, but you can reduce the weight. That's what Modification is all about, making something that's good, better.
Ok, but here we are talking about full stock Lexuses going on a track-fun-day! Not a few cars can do that (I had one and it was certainly funnier than an SC)
I haven't converted my SC yet. I'm still working on the suspension. You can take a Stock SC on the Track too, but then you'll realize how ridiculous your car is because it has to meet government and luxury specifications. That's one of the reasons why most of us want to modify. :)