There's two problems with these programs.
The first problem is that the people we're really talking about, the ones living/defecating/etc on the street do not want help.
The second problem is that in order to want to get better, an addict has to hit their personal rock bottom. Programs that keep people floating above their personal rock bottom are like family members enabling addicts. It ultimately doesn't help them.
It's VERY difficult to create social programs that help people want to not be ill, while simultaneously not letting them fall to their own rock bottom.
And then consider the position from the legislature of creating incentives for government programs/NGOs which align with the desired outcomes and it becomes expoentially harder.