The fact that the biggest complaint some fans have had with ROTJ is that Han survived illustrates how and why he is a secondary character-- he is expendable. You don't need Han to beat the Empire, restore balance to the Force, and all that jazz. If he had died in the movie, yeah it would've been sad, but the biggest thing it would've done is raise the stakes for Luke's conflict with Vader and the Emperor. That's the really important battle-- not the Rebel Armada attacking Death Star 2: Electric Bugaloo, or the teddy bear guerilla soldiering down below. Han is an important piece of the puzzle, but not an essential one, and by that count not a primary one.