If the top earners can easily keep more of their money, what's the incentive to create new job-producing enterprises, when they can just sit on the money?
if you have half a brain in your head, you would understand that the less you get to make and keep the less apt you are to invest in future enterprises. The risks rise with less to fall back on.
That has been the conservative talking point for as long as I can remember, and for the most part, it's bullshit. People who want to become rich will work as hard as they need to in order to achieve what they want. On the other side, many rich people get rich out of pure luck, and they really don't give a shit about the money; they just enjoy the success, so the tax rates have nothing to do with it. When I talk about people getting rich out of pure luck, it doesn't mean they didn't work for it, but many people just fall into things. Zuckerberg had a neat idea that became Facebook, but he could never have imagined what it would become when he started it as a social thing for students where he went to school. Many businesses start out like that. It doesn't mean the people who started them didn't work hard, but they did get lucky that they found/created something that worked. For every one of them, there are countless others who work just as hard and never catch the golden egg.
But back to the basic point; higher tax rates do not dissuade people from trying to increase their earnings or wealth. It sounds like a good argument, but for the most part, it's hogwash. I'm sure you can find anecdotal evidence of it, but overall it doesn't fly.