BARCELONA, Spain -- Many people use their smartphones to watch video, play games and wake them up in the morning. Some even use them to generate digital boarding passes to fly. So why not use phones to buy stuff at retail stores as well?

A variety of mobile wallet systems store credit or debit card information on phones in encrypted form, offering more security than standard plastic cards with magnetic stripes. To make a purchase, simply tap the phone on a card reader or wave a bar code over a scanner. There's convenience in not having to fish out your card.

Yet most people still prefer plastic.

Mobile payments have perpetually "been 18 months away from being big," said Kebbie Sebastian, managing director of Penser Consulting, a London-based payments advisory firm.

Use has been limited to a handful of retail stores, vending machines and transit systems around the world. A 2013 report from the Federal Reserve in the U.S. said only 6 percent of smartphone users had made such a payment within the previous year.

That isn't stopping proponents from making yet another push this week at the Mobile World Congress wireless show in Barcelona, Spain.

Visa and MasterCard plan to let phones with near-field communication chips, or NFC, access card information over the Internet. Before, the data had to be stored on a secured part of the phone and required the cooperation of device makers and mobile operators, which had competing payment systems.

Samsung, meanwhile, said its new Galaxy S5 smartphone will allow people to authenticate PayPal transactions with a fingerprint rather than a passcode. It comes as PayPal works on equipping merchants with wireless sensors so that repeat customers can pay while leaving their phones in the pocket.

And a startup called LoopPay recently released an iPhone app that works with a phone case or attachment to imitate the magnetic signals that regular cards produce when swiped. This way, retailers can accept app payments with standard card readers.

One of the biggest obstacles has been the lack of readers that retailers can use to accommodate mobile payments.

Avivah Litan, a security analyst at Gartner, said that's changing as U.S. merchants face a 2015 deadline to accept cards with security chips, which are currently more common in Europe than in the U.S.