Fast riding on the track is a test of your skill, fast riding on the street is a test of your nerve.
Fast riding is the same no matter where you are.
It takes skill to ride at top ten percentile on the street, just as it does on the track.
One may be smarter than the other but that doesn't make street riding purely about nerve.
It takes a lot of nerve to tip into a turn at 100mph street or track.
The difference on the street is the unknown.
A rider may have the skill to take a certain turn at 60mph: If it were duplicated at the track, he wouldn't have any problem at that speed. But as it sits on the street, it's blind and the apex isn't visible on approach. So 60mph is purely an act of faith. Faith that it goes where it seems to go, that the surface is clean, that there isn't an oncoming SUV with two wheels over the double-yellow.
On the track, those variables are mostly eliminated--radius is going to be the same as it has been all day, and if there's a hazard the flagger will warn you. Freed of those unknowns, it's your long-practiced skills that limit speed.
But in street sport riding, we have to make decisions about entry speed, line, etc. considering not just abilities, but also the unknowns and the consequences of misjudgment. In some turns, it may be possible to go as fast as in a similar turn at the track. In others, a poor sightline makes track speed a crapshoot, or a sheer rock face rather than soft runoff could turn a small error into a deadly one.
When I take those factors into account, I sometimes finish a turn with an unsatisfied feeling: "I coulda done that bitch 20mph faster!" Yup, Captain Hindsight, you coulda. Or, if the unknowns had worked out less favorably, you coulda turned in 20mph faster and ended up sliding on your ass, watching your motorcycle tumble over a cliff. That's just a tradeoff that's necessary on the street.