Probably the biggest threat to the unskilled and semiskilled workers has been and will be automation.
Here is a pizza maker
The recipe for a perfect hamburger
At my last visit to Panera sandwich shop I was greeted by a table full of ipad's to place my order. These machines replace some unskilled person or persons that stand behind a register take food orders. Since payment is "online" no paper tickets have to be processed, no money counted, less labor.
Virtually every dollar raise you give to a unskilled or semiskilled is one dollar closer to the cost of replacing them with a machine. Or the customer makes the brutal decision to go five miles out of their way to save $5-10 on lunch and avoid the employer who decides to be more generous.
If's not the fat cat business owner who is keeping the wages down, it's the consumer. I suppose there are a few customers who select a restaurant knowing they pay the trite term known as the "living wage". Maybe someday we will see advertisements like
"WE PAY OUR EMPLOYEES A LIVING WAGE"
Until that day comes small businesses must keep there costs down. Labor costs are the biggest expense for the food business. So keeping wages down is good business. Small business margins are tiny. Every dollar counts.