Money is a proxy for resources. If you boil it down to the essentials, income is the way we allocate the resources available to us to different individuals. It is not intrinsically a reward for work. It isn't even directly linked to work anymore in our capitalist system. The people who work the hardest don't have the highest income. The way the system currently works is that those with the most resources get the most additional resources, simply because they already have a lot of them.