BK78 your post is full of sweeping generalisations.
"let's be honest here, it's always possible to live on a reduced budget, not take holidays and buy expensive clothes etc. Our parents and grandparents generations didn't have the choice we have these days, and they seemed to manage on one person's salary."
I am going back to work in January. I should be FT but am trying to negotiate temporary PT, although we can't afford it. We don't have expensive clothes or holidays.
DH's salary pays the mortgage (on an ordinary 3 bed terrace), the council tax and the endowment/ insurances, plus the costs of his car to get to work. He can't get rid of the car because he wouldn't get back what he owes on it and he can't afford public transport costs on top of insurance etc. His travel costs are going up by the week but his pay isn't.
If we want "luxuries" like food, electricity, gas and water I have to work. End of story. We can't downsize because smaller houses are still selling for the same sort of money as ours (which isn't flash by any means) and there are already 6 of us here.
This was an unanticipated baby so we have financial commitments we wouldn't have taken on had we known. Boring stuff like replacement windows and a new boiler. But they don't just disappear because you've had a baby.
FWIW my parents lived on one salary because society was geared up to that. They could pay the mortgage on a house bigger than ours through my father doing the same job I'm doing now. I can't. My parents managed 2-3 holidays a year on that, and a car and a phone, at a time when most people had neither. Their furniture lasted a lifetime. Now it's designed to fall apart and be thrown away.
Not everyone who says they can't afford not to work is being awkward, and it may be easy for you to reduce your budget but it doesn't follow that everyone else can. You don't know what goes on in other people's lives.