Habit. The ones who do are the crowd who jump on anything that sounds like it's going to help the poor regardless of consequences or thinking it through. Yes, we are called to help the poor. That's why we have the St. Vincent de Paul Society and any number of other "in the trenches" groups. Charity should be from the heart, not government mandated, and that's what these people miss.
Those people want the government to help the poor so they don't have to. It assuages their guilt and let's them proudly say that they've done their part to help by paying higher taxes; just look at the Biden's charitable donations for proof. You won't find those people actually rolling up their sleeves and helping the poor though.