No kidding. It's intended for the blind, and using it this way is more like a well-supported hack than a feature.

However, Apple and Amazon's hands may be tied by contracts. Amazon tried to introduce general-purpose text-to-speech in the Kindle 2, but soon retracted it when rights-holders asserted that such a feature required paying a separate audiobook royalty.

Roy Blount Jr., in his role as the president of the Authors Guild, set forth that position in an NYT editorial titled "The Kindle Swindle". Noting the public opposition of the National Federation of the Blind, he specifically exempted assistive technologies.

http://www.nytimes.com/2009/02/25/opinion/25blount.html?_r=0

Perhaps the triple-click shortcut is turned off for some reason, though a quick search indicated that it was on by default in iOS 6 and 7. Normally double-click is enough to show all running apps.

You could check in Settings -> General -> Accessibility -> Accessibility Shortcut.