Progressive tax rates cause the government to continue to get an increasing percentage of income as incomes rise, therefore, reducing percentage of money for individuals to spend, save, invest, etc.
A tax break at that point gives people more money to spend or invest. The people receiving the money or investment have more money to spend, invest, or expand, and so on. So even though the tax percentage is reduced, money changes hands and is taxed more often. Therefore, the government can actually increase total tax intake by reducing income tax rate somewhat.
Some people don't have a grasp on that and think that the only way for the government to get more money is to raise taxes. But then that money just goes to friends of the polititions instead of circulating more broadly around the system getting taxed repeatedly.