Noah Smith writes a pertinent article but seems to miss a big point:
The fact of growing poverty in Japan shows that poverty is not causing the things Democrats say are caused by it, but that a third factor is probably causing both relatively low income in the USA and the problems associated with the same.
Once again I will link to a story about he poorest country in the USA and point out that you see none of typical problems there.
And to this about a guy who lives in San Fransisco on $7,000/year he evidently needs no living wage.
The Amish and Mennonites have low income too, without the problems associated.
These show that it is not about money or schooling, considering the groups above like to drop out of school early, though it might be about education (most of which occurs out of school).
I know some guys who so much more desired to sit home and drink or get high to working that more income would have negative social effects. I would like it if the country worked a little better for them but the solutions Democrats propose do not fit with that purpose.
I also know some people who manage to get along well on very little and so who do not get along very well on much more.
I have known folks on assistance who really needed it and benefited from it, so I am not all one way but let's not be naive.
The whole subject is fascinating to me.
BTW Bernie Sanders talks at lot about taking money from the rich and spending it on the middle-class and much less about spending it on the relatively poor, is that because he recognizes the above points? Maybe it is not just that they do not vote.