I'm reminded of what Terry Gilliam said on the Criterion dvd of Brazil. He was willing to include the "Love conquers all version" despite having fought so hard for his cut to be shown. He said something like how he saw plenty of things wrong with his film today but he wasn't going to touch it because that's the way he made it.
James Cameron wants the versions that he does not prefer to be included because he wants the audience to see why he believes that they are inferior, and how they compare to his prefered version of the film. As a sidenote, it's a fascinating insight into the filmmaking process.