The number of people watching video on their mobile devices turns out to be lower than many people presume.

Playing videos represented 40% of all traffic last year on worldwide wireless networks, used by cellphones and devices like iPads to access the Internet. That number is expected to grow this year to 60%, according to Bytemobile.

But, the mobile traffic management firm said, a study shows that only 10% of mobile device owners are responsible for 90% of wireless network traffic. The stat indicates that while high-profile products like Apple’s iPhone and iPad or Google-powered Android phones are gaining in popularity and usage, it will take years before the smaller screens become a major moneymaker for the studios looking to monetize the distribution of movies and TV shows to handsets.

Last month, Nielsen also reported that in the second quarter of 2010, only 10% of mobile users in the U.S. accessed video with their devices.

The report follows an announcement by YouTube last week that its mobile viewership has grown to 200 million views a day, up threefold over 2009.

It also comes as all the major mobile carriers are upping their networks to 4G, which can speed up the delivery of video and other programming to new smartphones hitting the market.