Why is water still above elements after draining hot water tank?
As been pointed out there will be some residual amounts of water left in the hot (and cold) lines even when the tank is empty. Which is you should open the valve farthest from the tank as it is being drained. The other problem I noted is that unless you have an immense (100 gl.) water heater or a very narrow drain valve the shouldn't take so long to drain. What might be happening is hard water deposits have collected at the bottom of the tank enough to slow and block water draining through the valve. Did you happen to notice a build up of whitish flakes on the ground? 

To check that the tank is completely empty and not just clogged at the drain valve: open TPR valve and connect the drain hose to a spigot and slowly reverse the water flow back into tank with a couple of short 'on/off' bursts. Air will escape through the TPR valve indicating that the drain valve is open.