Because they have to lose, it seems that many do not really have an idea of how trading or investing really works, by its very nature it is impossible that every single person wins at trading, if you are making profits with an investment that you made then that means that someone else is having losses, so it doesn't matter if the market seems as an easy way to make money the truth is the complete opposite of that and you cannot escape it.

The truth is that you need to be very consistent in the way you trade if you want to make profits in the market, and consistency is one of the things that people do not have when it comes to trading because they use their emotions when they trade and that leads to decisions taken by impulse.