The thing is, just because he's a bounty hunter doesn't mean that he knows much about the inner workings of the criminal underworld. Remember, as bounty hunter he's essentially a private contractor of the law enforcement world. Sure, he does work for criminals but I'm sure that he worked just as much for the Empire as well. Sure, working for crime bosses like Jabba would give him some familiarity with the criminal underworld, but he wouldn't be that involved with it since he would still be considered something of an outsider and not a regular part of Jabba's, or any other crime lord's regular crew, just his go to guy when he needs someone to catch or kill someone he wants caught or killed very, very bad.