When minimum wage workers get a bump in their salaries, this increase carries itself upwards to management in a ripple effect. Imagine a newly hired cashier who was once making $10/hour now making $15/hour, much more than you had once paid your best, most experienced employee. It’s only reasonable to think a general manager who was previously making around that number would require the same increase in salary, if not more!
As the result, restaurants will be forced to lay off employees, which they can only do to a certain extent before quality is affected. At that point, they would be forced to charge higher prices.