The first ever reference of the most dangerous job on the Galaxy was when Darth Vader called the Bounty Hunters Guild to track down Han Solo.
Boba Fett was the only one capable of accomplishing this hard mission. There's no telling where this fame comes from, has Boba only had three lines in Empire Strikes Back and less than 5 minutes in the whole Saga. But it is the most recognizable character and costuming fans find it the most interesting suit to build.
Even so, Boba is a though, hardcore Mandalorian and he is feared Bounty Hunter, known never to fail any given job...