New technology is upending everything in finance, from saving to trading to making payments.

When it comes to mobile wallets, Apple is the $1 trillion elephant in the room.

The iPhone maker controls about half of the US smartphone market and around 10% worldwide. A recent survey showed that more than 80% of US teens have an iPhone. Every one of those devices comes pre-installed with Apple Pay, the company’s mobile wallet.

Consumers in the US and Europe still like to buy things with debit and credit cards, but Apple isn’t giving up. As iPhone sales stall, the Cupertino-based company is looking to squeeze more profit out of services like payments. Among those efforts is its credit card, which is designed to reward customers more for using the mobile wallet than the flashy titanium payment card.

Perhaps the giant smartphone maker’s biggest advantage is its grip on the iPhone’s near-field communication (NFC) technology. Used by many companies, NFC is the tech behind contactless payments, among many other things. It has caught on in the UK for payment cards, and seems likely to become popular in the US over time. Google, which controls the Android operating system for mobile phones, doesn’t restrict access to NFC.

But on the iPhone, Apple for the most part blocks other companies and developers from using its NFC application programming interface (API) for their own products, including mobile-wallet apps. (One possible exception is a transit service in Japan.) It doesn’t take much imagination to think that this has likely impeded innovation. If you see someone using an iPhone for payments, they’re likely using either Apple Pay or a mobile-wallet app that relies on optical QR codes. QR codes are the dominant way to pay for things digitally in China, where WeChat Pay and Alipay are dominant, and are also popular in the Nordics via services like Sweden’s Swish.

Apple’s decision to restrict access to NFC is clearly a strategic one, said Tim Derdenger, who teaches at Carnegie Mellon University’s Tepper School of Business. The lack of access impedes startups as well as giants like Amazon, which operates Amazon Pay. “They don’t want rivals launching a wallet,” Derdenger said. “If they opened it up, it would mitigate their market position.”

Payment company executives Quartz has spoken with grumble about Apple’s stranglehold on NFC. But for the most part, they’re not willing to pick a fight with a company that has a cash hoard of around a quarter of $1 trillion. It’s better to be friends with the tech titan that controls the App Store and has deep relationships from Washington to Shenzhen.

There are some exceptions, however, such as a company called Twint, which has a service for QR-code payments. The Swiss firm complained to its domestic regulator that Apple was overriding its app whenever the iPhone was held near a payment terminal (the NFC reader automatically triggered Apple Pay).

Apple agreed to a workaround for the QR-code payment app. Twint’s chairman reportedly wanted Apple to go further, by opening up the NFC technology for competitors, but that still hasn’t happened.

“It would be desirable to be able to have an NFC interface,” a spokesperson for Twint said in an email. “In the meantime Twint has focused even more strongly on QR-code.”

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There are some sound reasons, such as security, for Apple to restrict access to NFC on the iPhone. “Apple is very keen on keeping customer information protected,” Derdenger said. “Nothing is more important than payments and money when it comes to personal information.”

Even so, the Android operating system allows NFC access, suggesting Google feels comfortable with the risks. Apple didn’t respond to requests for comment.

Two days after this story was originally published, mLex reported that the European Commission is revisiting this issue. A spokesperson confirmed in an email to Quartz that the regulator has requested information from market participants about competition concerns related to Apple Pay.

“The Commission monitors possible anticompetitive market practices and abusive conduct,” the spokesperson said. “The Commission is actively monitoring the development of mobile payment solutions, the behaviour by operators active in the payments sector, including mobile payments.”

A group of Australian banks tried to loosen Apple’s grip on NFC so that they could build their own payment apps using it. But the four lenders, which were seeking to negotiate collectively for NFC access, lost the battle in 2017. Australia’s competition watchdog said the banks’ collective efforts were more likely to damage competition than to improve it.

“Regulators are still behind on this, because these markets and platform markets and businesses are so complex,” said David Nieborg, a professor at the University of Toronto. “Will they go after Apple on this one specific feature? I think there are almost bigger fish to fry in that sense.”

Probably the best-known antitrust challenge to Apple is from Spotify, which lodged a complaint alleging that the iPhone maker was putting competitors at a disadvantage. The music-streaming company claimed in an EU complaint that Apple was favoring its own Apple Music offering in the App Store. Apple faces a similar challenge in the US, where the Supreme Court ruled in May (pdf) to allow iPhone users to pursue an antitrust lawsuit involving the App Store.

Europe’s competition commissioner Margrethe Vestager has taken a muscular stance when it comes to American tech companies. Her agency has considered Apple’s control over NFC access, but so far has “taken a very preliminary view that there is still enough competition in the NFC payments space, that there were other companies doing similar things,” said Ashwin van Rooijen, counsel at Clifford Chance’s antitrust practice in Brussels. Clifford Chance has also represented Spotify in its complaint against Apple.

Rooijen argues that Apple doesn’t necessarily face much competition after its customers start using its iPhone. It’s not easy (though it’s certainly possible) to get out of the Apple ecosystem once your photos, music, and credit cards are linked to it. He thinks it may be just a matter of time until European watchdogs revisit this issue.

“Clearly Commissioner Vestager has left the door open to further complaints,” Rooijen said. “She practically invited these formal complaints.”

This article was updated in the 13th paragraph to show that the European Commission is again probing Apple Pay competition concerns.