Who is switching to winter tires and steel wheels?

This is exactly what would be expected when going from 19" to 17" because the 17" tires have a taller profile.
Manufacturers simply follow demand with big wheels because it looks "cooler" or more "sporty", more "luxurious" etc. in the eyes of the average consumer.

Other than providing clearance for bigger brakes (Which could be negated if modern vehicles did not weigh so much) There is literally no practical benefit to bigger wheels with skinnier tires.

You can achieve the same handling/steering response with smaller wheels and thicker aspect ratio tires by adjusting tire pressure within reason. If anything, smaller wheels are usually lighter, offering an advantage.

The actual reason why the new tires felt softer and less precise was likely due to a combination that the tires still need to be broken in, they are winters with a softer compound, and a simple matter of adjusting tire PSI's.
 
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