“Despite much publicity upon launch, Apple Pay, Samsung Pay, and Android Pay have struggled to gain traction,” the analysts concluded. “Mobile wallet adoption has been underwhelming to date by nearly every objective standard, including initial penetration of smartphone users and repeat usage rate.”

While up to one-third of U.S. phone owners have enrolled in the payment plans, frequent usage is uncommon, the analysts said. Only 8%, 6%, and 3% of people use Apple Pay, Samsung Pay, and Android Pay at least once per week.

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What are the big problems standing in the way of greater usage? The biggest is lack of compatibility. One-third of the 100 largest retailers, including Walmart (WMT) and Kroger (KR), don’t accept Apple Pay and only 20% of smaller merchants do, the Goldman analysts noted. There is also no clear benefit to using a mobile phone to pay versus a credit card, with a lack of consumer incentives an confusion about which is more secure, they said.

“We believe most consumers fail to see a clear advantage in terms of ease of use relative to traditional cards (particularly magnetic swipes which take 2-3 seconds),” the analysts wrote.

The smartphone companies say usage is growing quickly. In May, Apple (AAPL) CEO Tim Cook said the volume of Apple Pay transactions worldwide had increased 450% from a year earlier. But as usual, Cook didn’t reveal the number of Apple Pay users, revenue from Apple Pay, or the value of those transactions. Neither Google (GOOGL) or Samsung has provided such specific details, either.

Mobile wallets will not get much more popular in the “medium term,” the Goldman analysts wrote without defining the amount of time they meant. But the products “stand a good chance of gaining traction in the long run,” they said.