Fighting homelessness is also something of a national collective action problem.  Improved local services tend to draw more homeless people to your city, demanding further resources.  Many homeless people have gravitated to big cities in search of opportunities lacking in their small home communities.  Other cities or provinces try to offload their homeless people on other jurisdictions, like the infamous bus tickets provided by the Alberta government in the '90s for welfare recipients.  Attacking the problem of homelessness on a national level could even out the burden, and possibly lead to better outcomes by helping people move to where the opportunities are.