"how come top racers don't ride 'em"
Kawasaki quite making them! I think it's all about $$$$.
The big guns tell the team what to ride, EPA coming down on manufacturers. Class rules in MX & SM.
I believe the 2 Smokes can run clean, but R&D costs money. Re-tooling, cost effective,yadda-yadda...
Downside? Parts availability, primarily. A gallon of pre-mix, (which is almost redundant compared to a top end service)
You could say they / We are bit of a Cult following, But whats wrong with that?
( It's all about the fun factor for me anyways) And a bit of Going against the grain...
As far as being comfortable on an open class bike has a bit to do with maturity (I think).
You can get in trouble in a hurry.
However I think you'll find these old girls are quite forgiving and with a minimum of work are at home in just about any environment you throw at them. Ice racing to Dune riding, Single Track to SM to Motocross & Hillclimbing,Sand Drags and Good Old PlayRiding. Sorry Mark, Land Speed racing takes a bit more than a sprocket & Exhaust Swap...