I don't think it's the norm, but I think it's quite common.
Our family income is considerably less now than it was 10 years ago before we had kids (I left high-paying job to retain as a midwife), and our family is twice the size it was! We went from spending whatever we fancied, to having a small, set cash budget each week and selling anything that wasn't nailed down to make ends meet.
The 3 years that I was training were godawful, and although I'm coming up to a year qualified now, we don't feel much better off as we're having to use the my salary to do all the things we put off while I was studying (replace dangerous kitchen, re-do rotting bathroom etc). But we don't go overdrawn. We use pretty much every penny we earn, but no more. I am a demon budgeter, every meal is planned, we waste nothing, I sell on everything the kids grow out of, and buy "new" stuff second hand.
Living on a reduced budget is a hell of a skill, and even as my pay rises (not by much, midwives are woefully underpaid!) I get really jittery if we spend too much, or overrun the weekly cash budget.