Why are rich people in the U. S. paying so low taxes for marginal rates?

The top 10% of earners in the U. S. control 90% of the annual income and 99% of the accumulated wealthy, yet they pay less than 70% of the income taxes. This is pathetic. It's robbing normal people to make the rich richer.
Why are rich people in the U. S. paying so low taxes for marginal rates?
Post Opinion