I suspect most users don't need that feature, but when you do need it, it's mighty handy. It's handy to be able to toggle visibility on hidden files. One of the features I use most is 'Show hidden and system files' under Finder options in the Finder tab. I'm not afraid of using CLI, but I'd much rather use the graphical user interface (GUI), which is really what the Mac was supposed to be all about. Tinker Tool does just what it says it enables the user to access and tweak various under-the-hood features of OS X, many of which you'd have to otherwise control using the command line interface (CLI) in Terminal.app.
