Well, that's because you aren't really familiar with the classical world. Menuhin has improvised with Ravi Shankar, with Stéphane Grapelli, Yo yo has played Jazz, with Mc Ferrin by the way (their album, Hush is gigantic). And improvisation, even though it arrives late in a classical musicians training, is covered. Not all of them succeed, but just like not every guitar player can play be-bop lines...

I agree with what you say, but it's sometimes easier to say that the classical trained guys can't play the blues and that's something we can do better than them...Because if they could also do that, what would be left for us right? Shawn and Allan express themselves on the instrument, but Shawn is classically trained on the piano, and Allan is coming from Mars, so he must have perfect pitch among other things (like extra muscles in his hands) :D