I agree in principle but I would venture a guess that number of two-income families that can deal financially with a loss of one source of income is very low.

the very first financial discussion I had with my wife (fiance at the time) was that we will always live off a single salary and 2nd salary will always go into future bucket (we tap in for larger purchases or fancy vacation here and there). I don’t think many families are setup this way though - in my limited personal experiences a loss of one source of income leads to sale of the house/condo and move (rent or downsize)