The natural movement of the stock market, in the long run, is up. Even when we see crashes in the market, the market will correct and move upwards again.
First of all, the natural movement of the stock market is up. Since the average return on investment historically is 7% per year, we can see that this is true for the past 100+ years.
When companies are in the market for a long time, they have matured. When companies have matured, they will most probably not provide you with an average annual growth of >10%.