On a recent Thursday afternoon at a Denny’s in Long Beach, Calif., a four-foot-tall robot glided toward Diane Deconnick’s table. Its three tiered trays could have hauled a feast, but they were empty except for a bowl of soup and a fried chicken salad.

As the machine rolled to a stop, a scrolling digital display announced, “FOOD IS HERE.”

“It talks!” Ms. Deconnick said. A Denny’s regular, she had been curious about the robot since it appeared a few weeks earlier. This was her first time being served by it.

Or partly served by it. A waiter had followed the robot. He took the food off the tray and put it on the table. “What’s your name, robot?” Ms. Deconnick asked. “Lily,” the server answered. He’d named it himself.

Ms. Deconnick, who planned on tipping her usual 20 percent, said, “I like Lily. She’s a good worker.”

For a decade, the promised era of robo-flipped burgers and automated baristas has always been just around the corner. But automation in restaurants, at least in the United States, remains a novelty. That is not because the robots and A.I. assistants can’t hack it. By and large, the technology is there, and in some cases has been for years.