Andus, it is possible to escape the earth's gravity without reaching escape velocity, going "slowly" as you say. However, this would be much less fuel efficient, since most of the fuel would be spent on the hovering portion instead of propelling the craft further from earth. Moreover, since more fuel would have to be burnt at higher altitude in order to keep the craft hovering, that same fuel would have to be carried along, requiring even more fuel to be carried through the lower altitudes. Below a certain speed, this would become impossible with conventional rockets, as the thrust of the rockets would be unable to lift the amount of fuel required from the ground. So, yes with a yet-to-be-invented light anti-gravity device with near infinite energy, you could slowly rise into orbit. Until then, we need to boost the rocket to escape velocity as low down as possible, burn up almost all the fuel (except that required later for maneuvering) and jettison the spent engine for additional weight loss.