Would anyone have seen Alien if it were titled Star Beast? Or The Breakfast Club if it were called The Lunch Bunch? Probably not. Although we'd still see Annie Hall if it went by its working title of It Had to be Jew. (Source)
Titles are important. One of the alternate titles for this film was Eddie Goes to Toontown. That's a terrible title, even if it is an accurate way to describe the film's narrative technique.
Eddie Valiant is our hard-boiled detective. (Well, this is a PG-rated picture, so maybe he's just soft-boiled.) But the film features Eddie in every scene. We follow him as he gets the gig from R.K. Maroon, takes pictures of Jessica getting her patty cake on, and then, eventually, tries to discover who framed Roger Rabbit for murder.
If the film showed us Roger or Jessica's perspective, it would spoil the mystery. By staying close to Eddie, we make discoveries with him. And we get to visit Toontown, too, which is a lot more colorful, zanier, and fun than the boring title Eddie Goes to Toontown suggests.