Imagine a scenario where you and your fellow cube dwellers could band together, go to your boss, and tell him “If you give us a big fat raise at the expense of the shareholders, we’ll give you a personal kickback.”
That’s what teachers’ unions do. The union members band together, package some payola in the form of union dues, launder it into “campaign contributions,” and give it to politicians who control the union members’ pay. In return, the politicians vote to increase the pay of the union members.
This is all at the expense of the taxpayers who have little say in the matter and are barely even aware of it. Unlike shareholders in a company, taxpayers don’t receive profit and loss statements. They just receive tax bills.