You got me! I guess I don't know why there is a need for one unless the rider is missing a right leg.
I have been riding for 49 years and haven't seen that mounted on a bike yet.
What are your thoughts?

 

I've seen people use thumb brakes at the track, but this actually seems dangerous and completely unnecessary. Even if you couldn't use the brake pedal for whatever reason, I wouldn't worry about it. The rear brake is pretty useless on a sportbike anyhow.

 

What's the benefit supposed to be? Is it something to do with stunt riding?
i read the description and it says it delivers 90% of the pedal's braking force rather than the 25% of the thumb lever. Not sure why you'd need more rear brake force on a sport bike unless it's for feet-up wheelies or something.

 

Its for stunting....

 

​​​​​​Makes sense. I don't do stunts, why is the thumb brake not enough?

 

I don't stunt either....