Most of the people in the world do not earn enough to make a good enough to put money aside and that is the problem. Majority of the world is living under poverty wages, which means that their salary is not enough to be considered out of poverty, they are literally in it.
This is a problem that billions of people around the world face. Those who are employees of a corporation usually only get a low wage that is only enough to cover their living expenses for a month. Only a few companies have high wages. So with a small wage they have to live as frugally as possible and leave some money to save and invest. But there are also many who are married and have children and this makes it impossible for them to save their money at all. This is the problem that makes it difficult for many people in the world to gain wealth by investing. Some people will not relate to this situation especially if they are not employees and come from a prosperous country. But for third countries being an employee means you only get a small amount of money to meet your daily needs, nothing more.