It's not that Android users don't use their apps, they do: Nielsen says Android users spend about an hour a day on their phone with two-thirds of that time being spent apps. It's that they're all spending their time in the same apps (probably because most apps just suck).
According to Nielsen's numbers, the top 10 Android apps accounted for 43% of all the time spent in apps. If you stretch it out to the top 50, those apps account for 61% of all time spent in apps. To quote Nielsen:
"With 250,000+ Android apps available at the time of this writing, that means the remaining 249,950+ apps have to compete for the remaining 39 percent of the pie"
That means for all the brouhaha in the app race prick measuring nonsense contest, it's so beyond stupid. No one uses that many apps. No one wants to use that many apps because most of the apps on the Market and the App Store are complete garbage. Surprise! We want to use good stuff. [Nielsen]