It is really amazing that is possible to get anyone to buy it knowing what must happen in the future.
The US budget must be balanced and the only way to balance it is to increase US taxes much higher. Capital gains, dividends, income taxes, and US corporate income taxes are going to have to increase. It won't happen for a couple of years but it will happen. When they are increased the after-tax return and corporate profits will decline and the stock market will plummet. At one time in the past the US had much higher tax rates, but it also had much lower stock values and higher pre-tax dividend rate. The stock market is a forecasting mechanism and looks ahead.
The alternative of running trillion dollar deficits forever to sustain the ponzi scheme stock values with more and more borrowed money is not going to work. At some point international investors will tire of buying US debt, forcing the dollar interest rates up, and the US government to balance its budget.