Around one-third of U.S. adults have apps on their phones, but out of that, only around two-thirds ever use those apps, according to a new survey conducted by Pew Internet. What’s more, the research organization found that one in ten consumers are not even aware that their phones have the capability to use apps, and only another tenth of the population have ever paid to download an app.

The survey was conducted based on telephone interviews with 2,252 adults in the U.S. aged 18 and older, with additional data from Nielsen’s December 2009 app download sample of of 3,962 adults.

Another interesting find from the survey is that apps rank relatively low on the list of most common activities on a cellphone. 76% use their cell phones to take pictures, 72% to send and receive texts, 38% to access the Internet, but only 29% frequently use an app. In fact, even video recording (34%) and music playback (33%) rank higher on the list.

The low figure for app usage may seem surprising given all the hype we’ve been hearing about apps. “On mobile devices, search is not where it’s at — consumers are spending all their time on apps,” Steve Jobs said at the announcement of Apple’s iAds platform back in April. So why the discrepancy?

On many phones, apps are a key feature. Most certainly, they’re emphasized heavily on packaging boxes, and at least on most iPhone and Android devices, they’re a mere couple taps away. But there are also many phones on the market that are less app-centric — they support apps, but don’t boast the hundred-thousand plus app figure in their every product announcement.

Also, with the amount of free apps out there — which seem to be growing even more since the prevalence of certain mobile ad platforms — some users may not see the need to pay for a number of apps they can find free alternatives for. The thinking: Websites are free, thousands of apps are free — why would I ever want to pay for something?

But whether or not apps are the most-used features of mobile phones, it’s clear that they are here to stay. Berlin-based Research2guidance recently forecasted that the worldwide smartphone application market will reach $15 billion by 2013. Steve Jobs, in the same iAd announcement event in April, noted that the company has paid out $1 billion to app developers. With money going both ways in increasing numbers, perhaps hitting the prime-time is only a matter of time?