Why do Republicans say that reducing taxes on the rich increases revenue, when it isn't true?

I'm not sure why people insist that this is true. Allegedly these benevolent rich people invest their money in the US and this creates jobs. Too bad these rich people don't even invest their money in the US anymore. Why would you when the returns in places like China are so much higher? So Republicans can extend the tax cuts for the rich and we can watch the money and jobs continue to leave the country.