I don't disagree that being able to live sustainably should be more affordable. In some ways it is, and where we can make those choices, we should all aim to do so, irrespective of income.
There was another thread a while away that suggested all low income families should be growing their own veggies for their families to live on. Nice idea, but when you're working all hours of the day and live in a high rise flat with no outdoor space, it's not going to be achievable.
"Have children only when you can afford them,
Spend within your means,"
I think this is advice we all should live by and don't see why you advocate low income family should be exempt.
Spend within your means includes taking on sensible debt when needed, in line with what you are able to repay.
However it's wrong to suggest that the high earning population should be funding low income couples consciously breeding large families that they can't afford, and the rest of the population having to fund irresponsible debt.
Interesting as it is, I think this argument is taking us away from your original point though OP.
Fundamentally, I think it's a sad state of affairs that anyone feels the need to prove that they contribute to society. For me it has nothing to do with income and everything to do with mindset, personal accountability and a shared sense of societal responsibility.