The cars without power steering had a more indirect steering gear ratio than the cars with power steering, otherwise even with the large steering wheel it would have been very hard to drive at low speeds.
In those years, an older generation of chief designers was in charge that saw car driving as sport and supposedly some work. Besides power steering,they deliberately opposed the introduction of automatic transmissions (a man has to use the clutch and shift, even full synchronisation was a frowned-upon compromise), air conditioning (want air? Open the window!), and window lifters (what's wrong with your arm?). All these amenities were forced on them by the US market, much later than they were available on US cars (e.g. 1955 Ford Thunderbird).
Klaus
1969 280 SL