Besides the high performance, the 600/750/1000 sportbikes’ ergonomics put your body in a very “unnatural” position – forwarding leaning, head down, arms low, feet backward and high – one that’s great for going fast on the track for a short time, but fatiguing for longer rides (stress on the neck/shoulders, lower back, knees), and makes low/medium control much more difficult for street riding. Also, the head down position (lower eye level) makes situational awareness more difficult on the street. The margin of error is low.
This is not to say that sportbikes cannot be ridden well on the street. A lot of people, including me, enjoy riding them – it’s thrilling and intoxcicating. You just need to know what you’re getting into, take the time, learn the basics on a smaller bike, learn the necessary additional techniques when you switch to a sprotbike, and, most importantly, keep the right head on your shoulders.