Stocks do not tend to go up, that would imply a greater than 0 return average for series. We instead get mean blur and skewness (which is actually often to the left).
The aggregate of the traded stocks, i.e. the market, goes up on average. That's why you make money by holding diversified portfolios.
The aggregate of the traded stocks, i.e. the market, goes up on average. That's why you make money by holding diversified portfolios.