Fair enough, but i cant see it, i personally think driving on the roads is far more likely to result in damage to your car than a trackday by your error or a third party, there are far more hazards on the road (trees, lamposts, kerbs, walls etc) and the greater speeds achieved on track are catered for in most cases with large run off areas. If your happy driving your pride and joy on the road insured, i see no difference taking it on track insured.
There have been a few posts of some pretty nasty crashes on here this last year, mostly spinning out, i would prefer my odds of spinning on track and coming off unscathed than that dude who ended up in a ditch on his roof for example.