The negotiating power of a company, which is practically a group of people, is much higher than that of employees, which are just 1 person. A big company loses what? 0.00001% of its revenue if it doesn't hire the right person for a specific position? An employee loses 100% of their revenue if they don't get hired or get fired.
So companies can pretty much do what they want (up to a point where they cause uproar and those individuals to bunch up into a group fighting the company).