Very interesting suggestion. I'm also not too familiar with the field, but it seems that most benefits are non-cash (e.g. health and housing), and cash grants tend to be <$1k/year [1]. I would guess there are many other reasons for the issues they face, particularly lack of integration into the broader economy.
As a counterexample, the Alaska Permanent Fund [2] is very popular, and economists have found it keeps thousands out of poverty.