Better theory; Fett is a shitty bounty hunter and Luke killed his aunt and uncle.
Its clear that Luke is not fond of living on the farm under the oppressive yoke of his possibly alcoholic uncle (he looks pretty trashed). So when destiny finally calls, he blacks out and kills them. Sets it up so that it looks like Tuskans did it. Ben however says its stormtroopers, so there is no counter argument or further investigation.
Luke is now free to roam the galaxy and kill thousands more as he tetters the brink between both sides of the force, with a sob story that no one in the rebel alliance would ever think to question. Ben, the only other person in the galaxy who was at least there is also killed, also strengthening Luke's sob story (Mentor and family killed by the bad guys). And poor aunt and uncle never get mentioned again.
Fett is just a shitty bounty hunter. Son of the galaxies greatest bounty hunter (At least if we include the prequels, though we only ever see him trying to assassinate someone, and that he outsourced), he's got some big boots to fill, and he just cant. So he makes up for it by being cheap.
Lord knows its probably the only way he gets work when its indicated that he's known for disintegrating his victims, which would make identification extremely difficult.
He only succeeds in his bounty because the empire did him a solid. Follow a junker filled with teenagers and a washed up smuggler? Too easy. Then he completely drops the ball and gets eaten.
Meta-wise, his popularity is based purely on great costume design. There is a saying that goes 'Bullshit baffles' and it pays big for Boba. Look like a badarse, don't say much and people just assume you're a badarse.
