system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why is the stock market necessary?

It seems like the stock market is a place where rich people go to make more money without doing any actual work. Maybe it used to be necessary for companies to get a start, but for already established company, what's the point? It seems to me like it just fuels greed.

EDIT: okay so it looks like I need to clarify a bit. So I understand the need for companies to have funding for more expensive projects. But realistically, don't these huge companies have enough money to afford this risk without relying on shareholders money? Essentially what I'm saying is maybe if there were some point where a company could be deemed as self sustaining it would no longer need to rely on shareholders. 


And as for retirement, maybe if people were more responsible with their money and were paid more reasonable wages, they would be able to manage their finances without essentially gambling for their future.
gpt
The stock market is a way of selling small pieces of your company in order to get more money for whatever you need.

As a company, you want to be big and successful (typically). If you want to expand your company and you need to make a GIANT profit, or it takes forever. So instead, you put your company on the stock market. You "buy"/keep 51% of all ownership to yourself, this way no one can do a "hostile takeover". This means 49% of your company can be "sold" to others willing to buy.

Rough example; 

So what happens is that you put you 1 billion dollar market worth company on the stock market. You create 100 million shares, you keep 51 million and sell the other 49 million shares for 10 dollars each. After 2 months, 10 million shares have been bought at the 10 dollar price. This means your company has made 100 million dollars. They use this money to invest in the company, making it worth more. So after 6 months, your company is worth 2 billion. So each share is actually worth 20 dollars now. People will notice your massive growth and expect it to continue; more people buy stock = more money for your company = more expansion etc.

TL:DR;

If you're a company making 1 million profit a year and want to expand, it takes years. Where as on the stock market, the company can make millions in a few weeks.