An Amazon promotion that allowed customers to deliver a $5 tip to their delivery driver maxed out in less than 48 hours thanks to high participation.

But not everyone was enthusiastic about the initiative, which launched on the same day Amazon got sued for allegedly stealing tips from its drivers in previous years.

The promotion only applied to the first 1 million "thank you" messages

In a Dec. 7 statement announcing the promotion, the e-commerce giant said customers could command their Alexa-enabled devices to "thank my driver" and the company would pass along the gratitude.

The top five drivers who received the most "thank-you's" would earn $10,000 to keep and $10,000 to give to charity.

"And, in celebration of this new feature, with each thank-you received from customers, drivers will also receive an additional $5, at no cost to the customer," Amazon said. "We'll be doing this for the first 1 million thank-you's received."

Just a day later, Amazon updated an FAQ on the promotion to say that the tipping portion had concluded thanks to "enthusiastic response" that met the 1-million-driver limit.

Customers can still tell Alexa to thank their drivers, and Amazon says it'll share the feedback, but drivers won't see a financial boost.

Amazon is also being sued over past tip fraud allegations

Skeptical social media users were quick to note that the promotion launched on the same day that Washington, D.C., filed a lawsuit against the e-commerce giant, accusing Amazon of stealing tips from its drivers and tricking customers along the way.

The suit revolves around the 2015 launch of Amazon Flex, which allows independent contractors to deliver Amazon packages in their own vehicles for $18 to $25 an hour.

The lawsuit alleges that, at first, Amazon Flex drivers would receive tips, which the checkout process added for customers as a default. But in 2016, the company quietly changed its rules to direct those tips into paying the drivers' salaries. In promotional materials, Amazon still assured customers and drivers that "100% of the tips" would go to drivers, though, technically, the money was subsidizing the company's labor costs.

The Federal Trade Commission brought the same claims against Amazon, and in a 2021 settlement, the company agreed to reimburse almost $62 million to drivers. Amazon also agreed to stick to its original pay model — letting drivers keep 100% of the tips they make — unless management gets explicit consent from drivers to change the formula.

In filing the lawsuit, D.C. Attorney General Karl Racine is asserting the company violated the district's Consumer Protection Procedures Act. Even though Amazon settled with the FTC, he says the company "escaped appropriate accountability, including civil penalties, for consumer harm."

Amazon spokesperson Maria Boschetti told NPR that the suit is "without merit."

"Nothing is more important to us than customer trust," she said. "This lawsuit involves a practice we changed three years ago [...]. All of the customer tips at issue were already paid to drivers as part of a settlement last year with the FTC."

Amazon employees still say working conditions are inhumane

Amazon has delivered more than 15 billion packages in the U.S. since its 1994 founding.

For millions of customers, it was the company's annual subscription service, Prime, that paved the way to robust online shopping habits. For the current cost of $139 per year, U.S. shoppers can receive free two-day, sometimes even two-hour, shipping.

But maintaining Amazon's delivery speed (and its customers' convenience expectations) involves a highly automated operation model, which, some workers say, is also inhumane.

The company's last-mile delivery drivers are paid an estimated average of $44,000 a year to deliver roughly 200 packages or more per day.

They say they sometimes pee in empty water bottles to meet their daily quotas. They regularly operate in extreme weather conditions, even on rough rural roads. And they suffer for it physically: More than 110 motor vehicle injury lawsuits were filed against the company in 2021 alone.

After years of such conditions, workers are fueling the company's biggest-ever unionization push.

They're being met by documented anti-union practices. Just a few weeks ago, the firing of an employee who tried to organize prompted a federal judge to issue a cease-and-desist order against the company.

There's still no easy way to tip your driver. Some shoppers are getting creative

Amazon didn't respond to an NPR question about whether the popularity of the "thank my driver" initiative was inspiring the company to make it easier for customers to tip drivers.

When NPR staff tried asking Alexa via an Echo speaker to "tip my driver," the system replied that "currently we're not able to tip them." The company does allow in-app tipping for its grocery drop-off service Amazon Fresh.

Several startups are reportedly exploring ways to build tipping platforms for Amazon drivers, but testing so far has stayed hyperlocal.

And whether those apps would see widespread adoption is another question. Overall tipping numbers appear to be on the decline in recent months, perhaps because of rising inflation or the end of pandemic lockdowns.

Yet, the growing awareness of delivery driver hardships is inspiring some customers to get creative.

In the popular reddit forum r/Amazon/DSPDrivers, drivers regularly post pictures of households that leave behind goodie carts during the holiday season, packed with packaged snacks, soft drinks and their own hand-written thank you notes.

"I love people who care!" one person wrote in the comments of a particularly festive cart. "It makes my blisters on my blisters feel better."

Another added: "Customers care more than the company."

Amazon is among NPR's financial supporters and also distributes certain NPR content.