#1 Already going to be two other coronations at WrestleMania

It's sad, but the truth is that despite the fact that there are three great babyface title challengers in Kingston, Becky Lynch and Seth Rollins, not all of them will be winning their respective championships.
While Seth Rollins is the most likely pick out of the three to lose, there's a very high chance that he will dethrone The Beast Incarnate, who isn't advertised for anything post-WrestleMania. Becky Lynch is basically a lock to walk out of the main event as a victor (and RAW Women's Champion).
WWE may feel that they don't want three different coronations in one night, which is why they may cut down one just to swerve fans. This would certainly be unfortunate, especially because it should be a night where all three superstars get crowned as champions.
All three of them undoubtedly deserve it, and it would be injustice otherwise.