Aside from buying IPOs, what exactly is the point of shareholders? The more I look at the shareholder system in modern capitalism, the more it starts to appear as nothing more then an otherwise meaningless system that allows rich people to profit off others work while providing nothing and holding no liabilities.

Of course, I will explain why I think this, then I want someone to explain to me why and how I'm wrong. What exactly am I missing?

A company sells shares in order to raise money from the IPO, however:


  
  Why couldn't you just use bonds and other forms of debt instead?
  Why should shares give shareholders rights beyond receiving dividends? Couldn't they justify buying the security on that alone?
  Why should the company act for their shareholder's profit? They bought an IPO (or, most of the time, didn't) and are receiving dividends? Why should they arbitrarily be given more?
  Given that major shareholders are often vary rich; doesn't this system just facilitate unhealthy levels of income inequality given how the workers are treated as liabilities to be minimised?
  What's the point of money making via stock buy-backs if smaller companies who could use the money to better compete (and thus help the market) are more rarely in a position to do this?
  Don't hostile takeovers using this system do nothing more then create frustration and monopolies?
  


Again, I get the point of the system, but how does having all this gunk help? Again, it just looks to me like a simple idea that was pumped full of crap that conveniently helps no one except power interests.

But as I said; am I wrong? And if so, how?
The shareholder system is a way of distributing the ownership of the company - each shareholder owns a certain part of the company. Shareholders are the owners of the company, in several company legal forms, such as an LLC. They exist before and after an IPO (Initial public offer), meaning that both public (traded) and private companies may have shareholders.

The shareholders can fire and hire the Management team (CEO/CFO/ etc), which answers your questions 2 and 3. They usually signal the Management team which actions they expect the company to take to maximize the company value, reflected by the share value. If the shareholders have a short-term gain objective, this might harm the long-term sustainability of the company - a case where the management team and the shareholders might have different perspectives.

Raising funds through the sale of shares is attractive for companies because it is interest free, and might give you access to much more funds than you would ever be able to get from bonds - depending on how a company communicates its future potential. However, this comes with a loss of ownership. There is only so much unsecured debt one can sell - and debt is always paid back with interest.