In an ideal world, we wouldn't give more benefits to people who were more well off.
To use a rather odd analogy, imagine you're playing an RPG that becomes extremely easy as you advance in the game. Enemies just dying within 10 ft. of you. That's a shitty game. Earning that one extra dollar on the margin as you climb the economic hierarchy should be more difficult, not less.
I hate this idea that people wouldn't be motivated to earn more just because it's more challenging to do so. What kind of pathetic excuse for a human thinks like that? Our society is backwards.