Back to basics with aerodynamics.
The horizontal tail flies as a little wing and with zero stick force during the early take off roll it will produce an increasing down/up force as V increases depending on the pitch trim setting. During this stage your little wing at the back end will be flying at close to zero angle of attack for minimum drag.
As you rotate you begin to change the angle of attack of the tail which opposes the rotation. It is stabilising. So if you only input a small stick force you will rotate only part way with the rotation rate decreasing towards zero as tail alpha inceases the wrong way to that desired.
So to produce a constant rate of rotation you have to input a rate of back stick input to continually and increasingly overcome the stability from the overall tail.
The whole thing is complicated somewhat by the increasing V and whether the tail is a slab or with elevator.
Not much different to pulling g for nose up pitch or into a turn.
The transition from rotation around the wheels initially to rotation around the cg at lift off should graduate smoothly as the wings increasingly take the load away from the wheels.