Actually, a rigid transmission ratio is unfavourable for all steering wheel positions, the steering should be sporty, and at the same time comfortable. In this case, sporty means that the steering should respond directly.
This means, a small gear ratio, but also a high amount of steering force. The other way round, a steering with a high gear ratio between the steering wheel rotation and the angle of the wheels, gives a very unclear
center position. For very small steering movements, a relatively large steering wheel rotation is necessary. The variable steering ratio combines the best of both worlds.
Of course one can achieve the advantages described above with an electronically controlled hydraulic-, or with a purely electrical solution. In this case, we're talking about a mechanical solution, which e.g., is also
possible for using in compact cars without power steering. While the gearing of the cog always remains the same, the tooth-pitch of the rack varies. It becomes continuously smaller from the center outwards. The
distance which the rack moves when the rotation of the gear wheel is constant, is smaller on the outsides than it is around the center position. Try it out if you like ... 12/10