Because being rich is measurable evidence that you are a better person than a poor. You have more ability to spend money, powering the economic engine, and capital to fund new ventures, either directly by starting businesses and employing people or indirectly through savings and investments.
A rich person in jail objectively harms society.
Maybe if we ate the rich and distributed their assets it would be an alternative?
If you are a company resource then you are a poor, and not an economic engine. True riches create companies and employ poors.