How about a person unable to work due to health issues? A single parent who isn't able to access highly paid work around childcare responsibilities? Or someone doing skilled but not well paid manual work, such as a joiner? Yeah, they're all just layabouts who can't be arsed to work hard and delay gratification, aren't they?
And there goes the assumption that people earning well can't possibly be one of those. I fell into one of these categories, as do many people I know.
I'm not earning £80K but I've done ok. I didn't when I was mid 20. At that time, I earned a Grand £600 a month doing an intership. No benefits, no financial help. I went from there. I became a single mum with no help at all, but continued to work FT, even though I wasn't entitled to tax credits and in the end of the month, I was hardly better off than if I'd opted to claim benefits.
Two teachers working FT will earn £80K after years. They just won't to start with. Two nurses will be close to it. The joiner could also end up doing very well by building his business.
When you decide to have 3 children or more, you are putting yourself in a position of vulnerability, not just because of the number of children, but the longer you limit yourself to not being able to work FT. Everyone is entitled to have as many children as they want, but deciding to have as many as it makes you happy and then complaining that you are not in as good a position as those who chose to stop at two and go back to work FT is ludicrous.
Some people are lucky to be where they are, some people are way they are because of pure poor luck, but in the vast majority of cases, people are where the choices they've made has taken them, happily or not.