This may be a smartphone age, but our lives are becoming a series of kiosk stops, from ATMs and supermarket checkouts to airlines and gas stations.

And now, increasingly, there’s the fast-food kiosk.

Kiosks have one main purpose: to save time. And an industry that dubs itself “quick service” has zero choice but to pay serious attention to any device that espouses to shave seconds—if not minutes—off each order. That might explain why such familiar names as McDonald’s and Panera Bread are spending millions of dollars to roll out touch-screen kiosks in stores.

Panera claims 60 percent of lunchtime transactions are completed on touch-screen kiosks at one bustling, Boston-area store near Fenway Park. That same 60 percent is what some of the savviest fast-food restaurants do daily out of their drive-thru windows.

“Kiosks turn a restaurant into a vending machine,” says Christopher Muller, professor of hospitality at Boston University. But instead of depositing coins, customers deposit their credit card.

Panera installed kiosks at that one location near Fenway Park back in 2012. Today, it has them in roughly 400 restaurants as part of its “Panera 2.0” platform, with plans to have them in virtually all of its 2,000 or so stores within a few years, says Blaine Hurst, executive vice president and chief transformation and growth officer at Panera.

“We’re seeing phenomenal results,” Hurst says. That’s because kiosk-using customers are generally happy customers, he says. They typically get their orders faster and, by a healthy margin, they come back to the restaurant more often, he says. That might explain Panera’s savvy name for its contraptions: Fast Lane Kiosks.

McDonald’s has gotten into the kiosk swing, too. Kiosks might not yet be at your neighborhood Mickey D’s, but it might be only a matter of time. CEO Steve Easterbrook, whose work to modernize McDonald’s is starting to show dividends, has publicly lauded kiosks—along with other digital technology—as being part of McDonald’s “experience of the future.” The kiosk experimentation began in Australia, but tablet-like kiosks have also rolled out to U.S. stores, originally under the “Create Your Taste” moniker, which was renamed “Chef Crafted.” These kiosks let customers design their own burgers, which are brought to the table by a crewmember.

Kiosks are empowering to consumers, say McDonald’s executives. That’s particularly true of smartphone-toting, app-wielding Millennials, who like nothing better than to take charge of the food scene. Kiosks, along with other digital innovations, “give customers control … of the restaurant experience,” says spokeswoman Heidi Barker.

While McDonald’s is coy about discussing its kiosk past, present, and future, Panera is not. “This will be our largest growth year for kiosks,” Hurst says. “Kiosks will probably be in most of our cafes within a couple of years.”

For Panera, it’s all about giving consumers digital ordering choices. When it rolled out the Panera 2.0 digital platform two years ago, it was a hearty mix of digital, mobile, and kiosk touch points. Even with smartphone app use exploding, Panera’s not cutting back on kiosks, but rather plowing ahead, Hurst says.

The biggest user of kiosks at Panera? Millennials.

None of this is to say that kiosk ordering at Panera hasn’t had some bumps and bruises along the way. Once in a while, a machine goes on the fritz. Sometimes enamored kids can’t step away from them. Other times, clueless adults stall the line by failing to quickly figure out how they work.

But when Panera first installs the kiosks at restaurants, it typically tries to avoid that traffic stall by temporarily placing so-called “kiosk ambassadors” on the floor during busy hours, preventing lines from bottlenecking, Hurst says.

At one Panera, he says, an enterprising general manager figured out the best way to get skeptical adults to use the kiosks: He personally showed them how to use the kiosks, and if any jammed up or slowed down, he whipped out his personal credit card and paid for the customer’s meal.

Kiosks face other consumer issues. Among them, says Boston University’s Muller, is germs. “They are terrible carriers of viruses and bacteria. Almost no one ever cleans them, especially in a restaurant environment,” he says. “Expect more food-borne illnesses to be reported as they become more standard.”

But Hurst says that’s not at all the experience at Panera, as crewmembers clean its kiosks regularly. Nor are customers expressing any concerns about kiosk cleanliness, he adds. “We’ve not heard from guests with that concern.”

Then there’s that 500-pound gorilla in the room: Aren’t kiosks really about cutting back on labor costs? “How much labor can we remove from the service package until customers finally decide that self service means no service?” Muller asks.

Hurst insists this is not at all the case at Panera. In fact, he says, Panera locations that have kiosks typically spend more on labor costs than those without them.

On the whole, customers mostly love touch-screen kiosks, Hurst says, adding that “the kiosk is basically an iPad.”

Which is why Millennials, in particular, can’t keep their mitts off of them. “Kiosks are a way for us to be even more isolated from random human contact,” Muller says.