It's not a tiny minority; at least in the US, ~1/4 mothers stay at home, or for mothers with pre-school children, it's ~1/3. It's actually quite normal outside of maybe certain urban professional circles, and spans low to high income.

I’m actually familiar with the 31% statistic and a very important wrinkle to that figure is it includes people on disabilities, retired, unemployed but want to be employed, etc. so we really can’t say “1/3rd of Americans live comfortable life on one income.”