A woman uses her smartphone. (Kiyoshi Ota/Bloomberg News)

In the past year, there’s been a flurry of experimentation with “buy buttons,” a way for social-media sites to allow users to purchase cocktail dresses, throw blankets, candle-making kits and sundry other items from retailers without leaving the social network. Pinterest launched “buyable pins” in June, the same month Instagram released its similar “shop now” feature. Those offerings joined ongoing tests by Facebook and Twitter for similar ­functionality.

The rush by tech giants and retailers to join the buy-button arms race would suggest that these businesses see money-making potential. And given how much time people spend on social media — an estimated 1 of every 5 minutes spent on a mobile phone in the United States is on Facebook or Instagram, for example — it would be logical to assume that these buy buttons are bringing retailers a blast of online sales.

But this holiday season, social channels accounted for 1.8 percent of overall online sales, according to data from Custora, whose software platform is used by many retailers. That’s just a tiny sliver of purchases, and it’s not even growing: In 2014, Custora found that social media led to 1.9 percent of sales during the same time period.

So what gives? Why haven’t buy buttons — or other features, for that matter — turned social-media sites into e-commerce heavyweights? And could that change down the road?

According to Michael Yamartino, Pinterest’s head of commerce, some of the challenge to adoption right now is a lack of knowledge.

“Awareness is a big part of it. This is a new thing,” Yamartino said. “Most people haven’t bought from a platform that’s not a ­retailer.”

And analysts say that there’s only a limited selection of items right now available for purchase via buy buttons, which may be a reason they haven’t exactly taken off yet.

Facebook, for example, is still in test mode with its buy button and is working only with small and midsize retailers. And on Pinterest, the number of buyable pins has doubled, to 60 million, since the feature’s launch — to be sure, a vast number. But it is still relatively small compared with the assortment on e-commerce giant Amazon.com, which some have estimated includes hundreds of millions of items. If shoppers aren’t yet seeing their favorite brands or even the price points they would usually spring for, they might not have much reason to give the option a try.

But even if buy buttons have not had an explosive launch, experts say they could prove to be a crucial solution to some of retailers’ biggest online shopping problems. Right now, stores are seeing a massive “conversion gap” on mobile devices, meaning that there has been a surge in the number of people browsing sites from mobile devices, but only a small share of them are actually making purchases. In studies, shoppers frequently say they don’t buy on their smartphones because it is a hassle to enter payment information and go through a checkout process on the small screen.

“The key players here want to be doing everything they can to reduce friction in the process,” said Andrew Lipsman, vice president of marketing and insights at ComScore. “The buy button represents their means of reducing friction.”

Buy buttons could also help retailers re-create the idea of the impulse buy for the online era. On the web, a shoppers’ journey so often begins with a search in Amazon or Google for a specific item. That has made it hard for retailers to do what they’ve long done in stores with elaborate window displays and sweet treats near the checkout counter: Persuade you to buy something eye-catching on a whim.

James Quarles, Instagram’s global head of business and brand development, analogizes that site to something of a digital store window, a place to potentially win a sale when customers are in “discovery phase of finding something and not probably even deliberately looking for it.”

Pinterest’s early experiences with the format suggest that buy buttons have potential. One of its early adopters, a clothing boutique called Spool No. 72, has found that some 84 percent of its customers who have purchased with buyable pins are ones that had not bought from the store before.

Yamartino said Pinterest can now confidently tell retailers that “this is going to be incremental sales with no cost.”

Kirsten Newbold-Knipp, a research director at Gartner, also uses the window-shopping analogy that Instagram invoked to explain the potential role that buy buttons could play in the future of e-commerce. But that’s also why she doesn’t see their arrival as a serious near-term threat to the likes of Amazon (whose founder, Jeffrey P. Bezos, owns The Washington Post), where people often go for routine purchases such as laundry detergent, or Google, where they turn to find a specific pair of Nike sneakers or Marc Jacobs purse.

Social media, Newbold-Knipp said, “is a different discovery vehicle than Amazon. It’s about serendipity.” 

There are plenty more reasons why buy buttons, and social shopping overall, might stumble. Retailers have been embracing social shopping because they simply want to get in front of shoppers in the channels those customers already frequent. But at some point, retailers could find that doing so requires ceding more control than they want to over a customer’s experience.

Scott Galloway, a professor who teaches marketing and branding at New York University’s Stern School of Business, said in an interview last year that because people go to social sites to keep up with friends,  they probably will not be in the mindset to, say, snap up a new pair of jeans in between commenting on their friend’s vacation photos.

Sucharita Mulpuru, an e-commerce analyst at Forrester Research, has pointed out that the chronological nature of Twitter and Instagram feeds might make it hard for a “shoppable” post to get noticed.