In addition to explaining his presence in the film, the story also explains the relationship that Fett and Darth Vader have.
Clearly, Boba Fett is useful and good at his job, however, he’s also a bit trigger happy and the big man doesn’t like that.
Boba Fett made no appearance in Star Wars: A New Hope until he was digitally inserted by George Lucas.
It’s a nice touch in the excerpt from Added Muscle (via The Des Moines Register) that Boba Fett says originally, he “wasn’t supposed to be part of this,” since originally he wasn’t.