It's cheap, especially for 24/7 joints such as many McDonalds or Burger King. Assuming a well built product, the burger flip robot will produce consistent quality at a workload a human cannot physically cope with, with none of the downsides that employees have (wages, vacations, sick days, inability to do the same task repetitive over 8h with no break)... that robot will pay itself off in two or three years, after then it is pure profit (maintenance aside).
The thing is, I (and many other lefties) would welcome a world in which robots do all the work while humans are free to do whatever they want - the problem is that in current capitalism, the burger will cost the same for the customer while the costs implode (most cost in restaurants is staff!)... meaning the extra profit goes to the owner class, not the worker class which has to fight for the few jobs that remain.