Why are left-wing activist groups so keen on registering the poor to vote?
Because they know the poor can be counted on to vote themselves more benefits by electing redistributionist politicians. Welfare recipients are particularly open to demagoguery and bribery.
Registering them to vote is like handing out burglary tools to criminals. It is profoundly antisocial and un-American to empower the nonproductive segments of the population to destroy the country -- which is precisely why Barack Obama zealously supports registering welfare recipients to vote.