I think the tax system in the USA is designed to reward people who form corporations and then get people employed. People who are employed don’t have as much time to work on reforming institutions, so giving a tax break for employing people makes powerful people’s lives easier. In order to keep this process revenue neutral, earned income is taxed instead of taxing business as much. After extracting money from people’s labor (since labor is clearly necessary in order to create wealth), the remainder of budget needs is made up from whatever resources are easily available (which is currently the assets of rich people, since they have been given a lot of money to get people employed).
How do things work? I provided my perspective, partly so that I could refer to it later, so it would be enlightening to learn about yours.