system
Given the following post, respond as if you're commenting on Reddit:
human
What use is having stocks to a company once their IPO is done?

As I understand it, a company sells a bunch of stocks to raise a lot of money for some investment they want to do, and then they forever either pay a little of their profits to shareholders as dividends forever, or they pay a bunch of it to them once as a buyback. But is there any advantage or use for the company in the stocks at this point? It seems not useful to the company to constantly be paying part of the profits to some outside person.
gpt
You seem to have the misconception that (1) the pre-IPO Company has no shares and the shares only exist after IPO, and (2) the Company exists to benefit itself. In reality, (1) the Company has always had shares since it was created (the act of incorporation is the act of creating shares), and (2) the Company exists to benefit its shareholders.

(1) When you register a company you create shares and then distribute them among the initial investors. In some cases that's just one person, and in some cases it might be a few people, each with a certain number of shares. When you IPO a company, usually you just create more shares and sell those shares to the public. Sometimes you don't even create new shares, you just sell your existing shares into the public market. 

(2) The "Company" exists only to benefit its shareholders. This is called a fiduciary duty. The objective of a Company is not to grow bigger or better, sometimes it might do that in order to better serve its shareholders, but it's not the actual function of the Company, which is to generate as much return for its shareholders as possible. Pre-IPO and post-IPO that doesn't really change, though the identity of its shareholders might. The IPO process might be used to enable pre-IPO investors to sell their shares at a good price, or it might be used to enable the Company to get cash to expand for the benefit of its pre-IPO investors.

(3) There's nothing stopping companies from raising more cash by selling more shares again at a later date. This is actually very common and can come in many forms (e.g. rights issues / convertible debt).