The knee is just a side effect of lean angle and using body position to alter the CofG. As tires got better, lean angles increased. In the 70's and earlier, the ''correct'' riding style was to stay vertical relative to the bike. I'm not even sure if they were taught to keep their eyes level with the horizon back then.
There's no weight on it or used as an angle gauge or anything like the myths say. It's just one of those things that happen when you're trying to move the CofG to stand the bike up as much as possible. It does look cool though. I can remember a few times coming out of the counterbanked carousel at Talladega, I'd be at full lean, knee on the ground, on the gas spinning the rear tire with the front tire in the air. That's probably the coolest powerslide that can ever be done. It was horrible on the right side of my rear tire, but I didn't care. lol
The part that I still find interesting to this day is the tactile feeling of how it feels when a knee is on the ground. There's truly no other sensation (actual, not emotional) that feel like it. Zero, zilch. I can't use words to describe it. It's just not possible.
