Came here to say what Mark C Still said below.

The one point I would I add is that focusing on broader, more inclusive issues enables a bigger coalition. Concentrating on alleviating poverty makes life better for poor people and poor people leading better lives makes life better for everyone else - less crime, less homelessness, less medical expense, less policing and incarceration, etc.

It seems way more politically feasible to get the middle class on board with poverty alleviation policies than with policies that target specific groups of poor people (and inevitably favor non-poor people who can claim membership of those groups).