ok let me reword my question! why dont they MAKE twist throttles for sleds. lol I know they have thumb leavers but is there a problem with a twist throttle in the cold?
Yes, you can put a handwarmer on a twist throttle. They make kits for them.
As far as twist throttles on sleds, powder snow tends to find its way into the throttle tube, which leads to stuck throttle ( I've done this in the past with a custom cable). From the manufacturers point of view, it is a safety issue.
The reason why Motocross bikes / motorcycles have twist grips and quads and sleds have thumb throttles is the way you hold onto the vehicle. On bikes you hold on with your legs, quads and sleds with ur hands/arms. twist grips are more easily controlled on bikes because ur not pulling and pushing on the handlebars like on quads an sleds.