Why is everyone so scared of amir khan??

First tim "headbutt" bradley called khan out and told him to "stop running" but then as soon as khan signed up for the fight bradley went completely silent and now its obvious he doesn't want to face khan, even for a career high payday! Then we have zab judah claiming he doesn't want to fight khan because khan is a "step down" which is hilarious as khan is clearly a step up from mabuza and matthysse! On the other hand, we have all these idiots commenting on how bradley and judah will destroy khan in a few rounds and khan has no chin etc etc. That being said, my question is this: if judah and bradley can destroy khan sooo easily, why are they not signing up to fight him??? they get a huge payday and another belt and an easy knockout win!! i suspect the true reason neither of these guys wants to fight khan is because both are aware khan is probably the best fighter in the division and they are more likely to lose to him than anyone else!