Capital gains on investments should be taxed at the same rate as ordinary income (or wages). It's only fair: it's arguably more effort to make a dollar in wages than a dollar through investments.
Why is this important?
Wages are taxed as ordinary income. Investment gains are taxed as capital gains. I assure you, having made both, that it takes more effort to make a dollar in wages than a dollar of capital gains. Capital gains should be taxed at the same rate as ordinary income. Investors will still put money in the stock market. (And only investors in startups and IPOs are really making the economy grow, the stock market has little to do with economic growth and jobs.) It's only fair.