walking up the hill is for when your bailout gear can't get you up the hill.
which happens when you try and use 11-21 on a 53/42 on a 20% grade.

26x34 isn't enough in the snow sometimes, because of the massive amount of friction from the snow build up on your fenders

that said, for me, in flat as a board, but sometimes windy toronto area, 34x25 is low enough, even for going up short 20% grades.

actually, in toronto and surrounding areas, you can get away with a 1x# setup with 39 or 42 chainring and 11-25 cassette and never run out of low or high range gear.