Probably has something to do with the sphere rolling from place to place. Moonbeam can be moved by functionally recasting it. The sphere rolls around. Not sure they have a mechanical way in the game to have it function as anything other than a familiar type summon and be able to move as it should. I suppose having it auto-despawn when combat ends would be a possible solution to this issue. Or as folks keep asking for, give us a way to manually break concentration on spells when we want to. Or both.
