Last summer, Uber at last started allowing its customers to tip their drivers. There was nothing actually preventing them from tipping before. At the end of the ride a passenger could have pulled out his wallet, fished around for change and handed the driver a few dollars. But it would have seemed absurd to do so, when everything else about the transaction was handled through a few taps of the app. The app didn’t enable tipping, so riders didn’t tip.

All of this highlights the conundrum for hotel housekeepers. Increasingly, people book hotel rooms through their computers or phones. They pay, and often pre-pay, with their credit cards. They get around town with app-based ride-hailing. There’s a good chance they don’t even carry cash. And yet to tip the housekeeper—or the bellhop or concierge—there’s no option but cash.

It is probably no coincidence, then, that tips are tight for housekeepers. According to the New York Times, fewer than one in three hotel guests in America now leave tips for the people who clean their rooms. It’s not as if hotel guests can’t afford them. The American Hotel and Lodging Association, which represents hotel owners, recommends tipping $1 to $5 per night. For a $200-a-night hotel stay, that’s the equivalent of taking a bag of M&Ms out of the minibar. 

Hotel pay varies widely, but some housekeepers rely on tips for their livelihood. The median housekeeper last year made $11.37 per hour, but in some cities it can be as low as $10 an hour. An extra few dollars a day in tips from a handful of additional guests could represent a substantial boost to those earnings. After the Marriott chain started leaving envelopes in 160,000 rooms for housekeeper tips, tipping seemed to have increased, according to the Times. But Marriott ended the practice a few weeks later, finding it to be unpopular with guests, some of whom felt pressured into tipping. 

A better solution would be to go the Uber route. Upon checkout (or electronic checkout), guests could be asked if they’d like to tip their housekeeper. This would be similar to what happens at the end of a ride on ride-hailing apps, or on receipts or tablet screens in restaurant and retail transactions. For guests who pre-pay, they could even be asked in advance. 

People in the service industry sometimes prefer cash tips, since they can be claimed quickly and directly, whereas credit-card tips don’t get processed until the next paycheck and can sometimes get fees deducted. But everyone prefers a slower, smaller tip to no tip at all. And in our increasingly cash-free world, those are becoming the realistic options.