Why not tip the people? They're not making $15 an hour. McDonald's is making a lot of money they're not sharing with their employees.

Feel free to tip if you have the desire and they are willing to accept it; it's just not standard practice as it is with waiters in restaurants (who rely on tips almost entirely for their wages). You would have to use cash, as they have no protocol for charging people's credit/debit cards for tips. Keep in mind that low wages are far from exclusive to the fast food industry. People who work in stores, people who do manual labor, low-level office/administrative workers, etc., commonly make similar wages. It is a rampant nationwide problem, not specific to a certain company or profession.