This is how incentives are currently structured to play out. If a company makes some money, it can either re-invest it to grow the business or pay it out as dividends. Dividends are taxed as income while capital gains are taxed much lower. This discrepancy in tax rates is explicitly to promote growth.

This is one area I think the left has missed the forest for the trees with the "tax the rich" slogan. The uber-wealthy aren't uber-wealthy due to high incomes. Steve Jobs famously had a salary of 1$. A higher tax bracket or 2 would barely affect them. You need to tax capital gains as income to actually make a dent. This would also impact a lot of middle-class retirement accounts though so nobody wants to do that. I think a proposal that bolstered social security to make up the difference for retirees should be combined with a proposal to tax all capital gains as income. I haven't done the numbers, but I bet that the extra tax revenue would more than pay for the extra social security spending.