WWE wanted The Undertaker in tonight’s draft and since he’s under contract, he cannot stop them from using his name/likeness. But he’s still insisting that he’s finished and asked not to be drafted. With the brand extension being re-implemented, it would be really difficult booking wise and ultimately made no sense to include him.
The plan right now is to allow “inter-promotional” Raw vs. Smackdown matches at the “big four” pay-per-views but it’s still going to be much easier to develop rivalries between talent that are already on the same show.
Triple H didn’t want to be drafted for the same reason. He’s planning to wrestle at Wrestlemania but with everything up in the air right now, there is no opponent in mind. This also relates back to Undertaker. While Vince wants to do John Cena vs. Undertaker, Undertaker hasn’t agreed to return, so it would be silly to plan draft moves around a hypothetical plan.