Price - Cost = Profit

Shareholders take their cut from the Profit side. Under the capitalistic owner-worker relationship, workers take their cut from the Cost portion. Customers want to minimize the price.

The shareholders and the workers are directly in conflict, and the shareholders are the only ones who get to appoint the board of directors. Shareholders want to maximize Profit, which means they want Price to be as high as the market can bear, and Cost (including workers wages) to be as low as the market can bear.

This directly, mathematically, incentivizes shareholders make things worse for workers and customers, and then roll those profits into the next business venture. Clever lawyers can justify their Cost by saving bigger Costs, as can lobbyists. Heck, if you're clever enough you can get legislation drafted to specifically target your competitors. Every antitrust law just invents a new fun little puzzle for clever lawyers.

The difference between a government and a company, is that I can vote out the greedy people in my government. I can't vote out greedy shareholders. Both will eventually become corrupt, but only one is built with countermeasures.