In all likelyhood because of his entirely different skill set. Moreland is a smaller duplicate of Cauley-Stein. Not that there's anything wrong with that, and I'm somewhat surprised that they waived Moreland, but something was going to happen one way or the other with the august first date looming. I think I'll wait to see if there's a wink/wink agreement between Moreland and the Kings. They have invested time and some money into him, so it's very possible he'll be invited to camp and given a chance to play his way onto the team. Of course that doesn't preclude another team from jumping in and trying to steal him away.
Look, the Kings could have another deal in the works and needed to keep a roster spot open in the event they're able to pull it off. If they still have the 2.8 mil exception left, and it's likely that they do, then there could be something in the works. Waiving Moreland could be nothing more than keeping that option open.