Restaurant customers are quite sensitive to price increases. This is why restaurants sometimes reduce the size of meals instead of raising prices.

In any case, the real reason for the article and its complaints about a "tight" labor market is to lobby for low wage immigration:

"Our industry is very much in need of a temporary visa program for the low-skilled, essential workers,” said Shannon Meade, the National Restaurant Association’s director of labor and work force policy. "

Translation : pretty please send cheap labor our way; our profit margins aren't high enough.