Robots are asking for tips. But who actually gets the money?

Machines are sticking out their digital palms. Your reaction could help shape the future of the service industry. If you're not in the mood for slot machines at Las Vegas's Venetian Hotel, you can find some entertainment at a bar called The Tipsy Robot. It has a kitschy gimmick: two robotic arms that make automated cocktails. I hit "margarita" on a screen and watched them jerk to life. They mixed tequila with lime and triple sec, spinning needlessly for extra flair and bowing to deliver the glass. It might have thrilled me 20 years ago. Today, it's almost a cliché. The drink ran $17 (£12.55), but I found an additional charge: a 10% "service fee". Tipsy wanted a tip. It wasn't the first time I'd encountered this. A similar robot barista asked me for a tip at Artly Coffee in New York. At Newark Liberty International Airport, a self-checkout machine suggested a gratuity on a bottle of water at an unstaffed kiosk. Across the country in Portland, Oregon, a human took my order at the restaurant Top Burmese, but a robot server wheeled out the dinner. For the human waiter, I happily tipped 20%, but on the other occasions I hesitated. The rules of tipping go out the window when robots stick