In general yes, but many many people are doing this to attempt a "normal" home the likes of which they grew up in, and that they themselves want to raise a kid in.

OR consider a household where 2 incomes of around 150 were earned when the house was purchased, but now one earner is not earning appreciably any more...maybe a stay at home parent or illness or whatever.

Again just saying some possibilities, not the normative experience.