The top 10% of income earners pay the majority of the income tax. So, when you have a tax cut, they get the majority of it. It's simple math. The percentages are the same, but the cash pile is bigger.
Actually, that's not entirely the case.
When it comes to the top 10% of income earners in the United States, you'll notice that they have far more tax exemptions, deductions, and tax shelters available to them. For example, Trump's tax plan hit teachers hard. They used to be able to write off the purchase of school supplies for their jobs, but now they can't. While if a wealthy person holds one business meeting on a yacht, they can write the cost of the yacht off as a business expense. Essentially, while the top 10% of income earners pay the majority of taxes on paper... after all exemptions and deductions, most don't pay anywhere near the percentage someone in the middle class pays. Many wealthy people have tax lawyers who have whittled their income tax way down to being below 5%. If you paid more than 5% of your income in income taxes, you paid a greater percentage than most of those in the 10%... including many corporations. For example... Amazon paid 0% in corporate income taxes last year. Yep, you paid more than Amazon! LOL
Many of these corporations get federal subsidies (corporate welfare). After their exemptions and deductions, if we include the subsidies, they actually drew a profit! At the tax payer's expense, of course.
Ah... and then there are the overseas bank accounts, and corporate address farms. All that money they "save" after reducing their taxes typically doesn't go into higher wages and better employee benefits. They put it in foreign bank accounts where it is sheltered from taxation and counted as pure profit.