The promise of a tip — that familiar 10 to 20 percent optional add-on for a meal or a ride — might be enough to lure Ryan Rich Moe into the driver’s seat for Uber again. He stopped driving for the popular ride-hailing service earlier this year because he was not making enough money. But Uber, which had resisted tipping for years, announced this week that it will start allowing the practice in some cities and then nationwide.

“That would get me back,” said Moe, who drives in Minneapolis.

Uber’s surprise decision to allow tipping is the latest twist in the nation’s conflicted and often ambivalent attitude toward paying just a little more for good service. The restaurant industry has seen a push by some toward no-tip policies, with mixed results. New technology, the growing prominence of the “gig economy” and changing views about which jobs qualify for tips have further clouded the propriety of a gratuity.