Businesses need capital to startup and grow. A key way to stimulate more investment in businesses is to make risk-taking attractive.
In Communist China, there is no tax on capital gains (whether assets are held long term or short term). They figured out that taxing investments less leads to more investments.
In contrast, President Obama wants to raise the current capital gains tax rate from 15% to 20% (or maybe more). This just doesn’t make any economic sense.