This piece originally published on Forbes.com.

Mobile has rapidly evolved from being a separate banking channel to becoming the hub of personal finance. As we noted in a previous post, Bain & Company recently surveyed 114,700 consumers in 17 countries and one question we asked was, What would you miss more for a day, your wallet or your mobile phone? Some 54% of US consumers chose the phone, and in China and South Korea, that share rose to more than 75%.

Mobile matters because it directly influences customers’ loyalty to their primary banks. And loyalty pays off: Loyal customers stay longer, buy more and refer their friends and colleagues to the bank. Bain’s found that bank customers who are frequent mobile users are 40% less likely to switch banks than those who rarely use mobile. Using mobile apps for routine transactions, such as depositing checks, delights customers more—by 32%— than making routine transactions in a branch.

The survey also highlighted how today’s branch model is obsolete. While bankers typically believe that frequent branch visitors are their most loyal customers, the opposite is true. Customers who use branches frequently are almost three times more likely to switch banks than infrequent branch users. Perhaps this stems from the fact that a branch visit is more than twice as likely to annoy customers as a mobile interaction.

For actual purchases of banking products, the branch still dominates, but several countries show the potential of digital channels. Of consumers who bought a banking product during the past quarter, 57% in the Netherlands, 55% in the UK, 42% in India and China, and 33% in the US did so using mobile or online devices.

The pace of mobilization varies dramatically from country to country. The Netherlands and South Korea have the highest mobile adoption, and Japan has the lowest. Some banks have made exceptional progress and point the way for others. After launching its mobile app in 2011, for example, mBank in Poland has continued to innovate. Customers can access basic financial information without logging in, obtain one-click loans with 30-second approvals and disbursements, and make peer-to-peer money transfers using the contact list in their smartphones.

The biggest threat to banks’ profit pools, though, comes not from other banks but from financial technology start-ups that are devising better ways to deliver banking services through mobile. Much of the industry’s attention has focused on companies based in Silicon Valley, such as LendingTree, Betterment and Apple Pay. Yet these Western insurgents have not managed to achieve large scale or the coveted network effect in their banking and payments offerings.

Chinese insurgents such as Alipay and WeChat, meanwhile, have leapfrogged the West. Some 600 million active users of Tencent’s WeChat messaging app can pay merchants and utilities, send money to friends, deposit investments into money market accounts, book travel tickets, borrow money and carry out other daily financial transactions with just a touch or two. This example illustrates how payments, commerce and social media have converged. More than half of WeChat users open the app at least 10 times a day, and purchase volume through WeChat Wallet has been 11 billion yuan ($1.7 billion) to date.

Other messaging platforms such as WhatsApp, which has 900 million active users and was acquired in 2014 by Facebook, also aspire to add similar broad wallet functionality, further pressuring banks.

If banks can master mobility, they’ll be able to shift to a leaner model designed for efficiency and to delight.

Gerard du Toit and Maureen Burns are partners with Bain & Company’s Financial Services practice.