What car do you have without power steering? Or, are you referring to electric as opposed to hydraulic power steering? I haven't seen a car without power steering since the early 00s (which was a 90s car).
The steering deadzone is not purely a function of power steering. Some of it is design or could be attributed to that, but a bunch of it also comes from slop in the physical connections in the steering column, as well as the suspension bushings, your tyre profile, etc.