The thing is: If the plane (or more accurately, the wing) is sitting at a negative angle of attack, the oncoming air is actually holding the plane down on the ground.

Think of putting your hand out of a car window - when you point your hand down, the air pushes it down - the same thing will happen to your plane.

You then need a lot of speed so the elevator can overcome that downward force enough to rotate to a positive angel.

But when you're sitting at a positive angle to begin with you don't need that extra speed.

Now, of course there's such thing as "Too much of a good thing", so you don't want a LOT of positive angle or the plane could lift off before it has sufficient flying speed- the plane should sit level, or SLIGHTLY positive