Stores that do not accept cash are on the rise, from quick-service lunch spots to Amazon's Go stores.

Not accepting cash can speed up lines and make life easier for card-carrying consumers.

But a backlash has grown, as the cashless trend leaves out lower-income customers who may not have a bank account.

Massachusetts, Philadelphia, and New Jersey have already barred stores from rejecting cash as payment, and New York City and San Francisco are considering similar measures.

This could affect the growth of Amazon's physical stores, which do not accept cash.

Cashless stores are becoming controversial.

Stores that do not accept cash are on the rise, from quick-service lunch spots to Amazon's physical stores. Not accepting cash can speed up lines or eliminate them altogether, making life easier for card-carrying consumers.

Not everybody is on board with this cashless utopia, however. Backlash has started, as the cashless trend leaves out lower-income customers who may not have a bank account. As of last year, an estimated 15.6 million people in the US do not have a bank account.

Philadelphia barred stores from choosing not to accept cash in early March, becoming the first US city to do so.

"Most of the people who don't have credit tend to be lower income, minority, immigrants. It just seemed to me, if not intentional, at least a form of discrimination," Philadelphia City Councilman William Greenlee told the Wall Street Journal.

New Jersey later followed with its own measure, which Governor Phil Murphy signed into law on March 18.

"This idea of 'we don't want to accept cash' just marginalizes the poor, young people who haven't established credit yet, people who prefer to pay in cash," Assemblyman Paul Moriarty, a sponsor of the bill, told WNYC.

Lawmakers in New York City have been considering a similar measure since February, while a similar proposal in San Francisco is also on the table.

Massachusetts is something of a first mover on this issue, having barred stores from rejecting cash as payment for decades.

A ban like this would predominantly affect chic lunch spots like Sweetgreen, but also Amazon's nascent physical store footprint. None of Amazon's stores accept cash unless required by law.

Read more: Amazon is closing all 87 of its pop-up stores, reportedly laying off all employees

In fact, the whole point of Amazon Go, the chain's tech-powered cashierless convenience store, is that there's no need to pay a cashier. Customers can just swipe their app and go. The store's cameras and sensors will see what you take and charge you accordingly.

If it becomes law, San Francisco's measure is likely to have the biggest impact on Amazon, as the company operates two Go stores in the city and has a third on the way. An exception for Amazon was removed in the most recent version of the bill.

"They can afford it," District Five Supervisor Vallie Brown said in a San Francisco Board of Supervisors meeting.

An Amazon spokesperson declined to comment to Business Insider.

Amazon had reportedly expressed concern about the law in Philadelphia, telling the city's department of commerce "several times" that it would not open an Amazon Go store in the city if the law passed, according to the Philadelphia Inquirer.

Philadelphia's law also intended to leave a loophole for Amazon.

The new law does allow for a store to use only app-based transactions, but only if a paid membership is required to shop there. You don't need a paid Prime membership to shop at Amazon's Go stores — only an Amazon account — eliminating the potential for a loophole.