PayPal is revealing some new numbers today about One Touch, a feature that lets customers make online purchases with the tap of a button.

Eight months ago PayPal rolled out a tool called One Touch that eschews the normal checkout process of typing in billing credentials in favor of tapping a single button to make a purchase. Six months after rolling it out earlier this year, 10 million people had registered to use One Touch.

The feature only works at participating web and mobile retailer sites, but PayPal has about a million merchants signed up, giving customers plenty of places to shop. Still, it’s hard to say whether this represents rapid growth for PayPal. The number of One Touch users is just 6 percent of its overall user base.

But it’s not just PayPal that isn’t seeing mass adoption of its one-button payment feature. Similar payment technologies are having trouble getting users onboard.

One Touch is very much part of a growing movement to capture and convert web and mobile shoppers into hard sales. For many years, online retailers have been plagued by shopping cart abandonment, wherein a customer will fill up their shopping cart with goods and then decide against the purchase right when they get to the point of having to fill out their debit or credit card information. This user experience hurdle has made designing appealing mobile shopping apps all the more difficult.

“The value proposition [for One Touch] is much stronger on the mobile device,” said Bill Ready, global head of product and engineering at PayPal.

As more people shop on mobile, more innovative payment options are becoming available. In addition to PayPal, there’s Apple Pay and Android Pay, both of which allow users to make in-app purchases on their smartphones. On the iPhone 6 and 6 Plus, shoppers simply need to scan a thumbprint to complete a sale.

Despite this, Apple Pay has had slow adoption too. Since launching a year ago, roughly 16 percent of eligible users — or 3.6 million people — have tried Apple Pay once, according to estimates from PYMNTS. Though the study largely focuses on examining how often people use Apple Pay at physical retailers, it indicates a low general awareness of the product.

And that may be the crux of the problem. Financial tech products con be confusing. For instance, many PayPal users can already check out pretty quickly at online retailers where PayPal is accepted. The difference between checking out with PayPal and checking out with One Touch is pretty minimal. In one case you log into PayPal with a username and password, and with One Touch you just hit a button. In order to capture more users, PayPal and others will need to make the value proposition clearer to customers.

Update: this article has been corrected to reflect that PayPal One Touch amassed 10 million users within its first six months.