Where do you get the idea that most revolutions have been a a disaster? Your concept that only incremental improvement is valid seems counterfactual and naive. You are just dismissing anything that you do not understand out of hand without even considering it.
Add to all this the fact that they fail with alarming regularity, and America's collective lack of enthusiasm for that option is perfectly understandable. I mean, historically speaking, for the average person, revolutions either failed, and you were worse off. Or revolutions succeeded, and you were worse off.
It's so bad that, again, people are even a bit skeptical even of low risk options like tax reform and stronger unions. Right now, people seem to view anything that even appears to move away from the status quo as dangerous because of the admittedly horrid track record of revolutions, combined with the off the wall proclamations and actions of certain groups opposed to the élites. (Believe it or not, you don't allay peoples' fears of a reign of terror by shooting up churches and Walmarts for instance.)
Incrementalism works great in periods of relative stability. In other contexts it can be dangerous and inhibit necessary action.