The incentive to provide benefits is to buy votes. If it doesn't buy votes for them either way because they are mostly voting (D) no matter what, then there's not much carrot to provide them, and since money doesn't come from thin air a distinct possibility you will end up selling the vote of some of the people you tax it from.
> A Representative represents everyone in their district
In theory, maybe; in practice, very much not; its one of the strongest arguments for having a system that has proportional representation (whether with small multimember districts or at-large proportionality or a hybrid system like Mixed Member Proportional.)
