Alternatively: it's good to see what's out there so that when you do (inevitably) write your own, you know /what you want/.

Just as a counterpoint, I've realized recently that using other things before making your own changes what you'd make, and not necessarily in a positive way. You find yourself thinking in terms of the constraints and features of what you've used, rather than starting with a blank canvas and coming up with something you haven't seen before.