Back in the 50's, 60's, and early 70's, the rubber used for winter tires was the same or close to the rubber used in summer tires. Winter tires had aggressive tread patterns and were often very noisy.
And the winters were often more brutal with more snow than we have been getting in recent years. If you wanted a winter tire that griped on ice you required studs. And more people carried chains compared to the number of people who carry them today.
Front wheel drive vehicles were very rare, Olds and Buick had some, but those models were very uncommon. In those years I never saw anyone run 4 snow tires. Even if you did, the front tires would still slip on ice because the rubber had no grip on ice. It seamed that the tread design for the front tires in the winter was about having parallel groves and the front were for getting water to clear the tread and for turning.
It was common to make sure the front had plenty of tread, but they were not snow tires. Spin outs were more common. Part of learning to drive in the snow was to go in a parking lot covered with snow and do some hard turns and doughnuts just to get the feel of how much power and speed the tires would handle before you would slide.
While running studded tires on all 4 with the older tire designs may have had more traction on ice back in the 50's, 60's, and early 70's, than the snow tires of today, studs were not allowed to be ran in certain months, and some areas did not allow you to run them any time. Studs would often leave the tire during the second year of use, or if you spun the tire. And chains would break if you ran them on dry ground.
----------------------------------------------------------------------------------------------------------
Now days the improved rubber compounds and tread design of todays snow tires that actually have some traction on ice makes running 2 a bad idea, regardless if the vehicle is front, rear, or 4WD.
However I feel much safer with 4 of todays dedicated winter tires on a vehicle, than I felt with the tires we ran on vehicles decades ago.