No. I could find, evaluate and install that package quicker than I could write the code that carefully. And the second time I need it, it's just "remember, install". Also, keeps my code small and focused.
Do you not read the code of packages you're including in your projects? I usually do at least browse through the "beef" of the code for anything I consider adding as a dependency. And try to figure out what's the level of maintenance I can expect, history of bugs, sometimes try to contact the authors, etc.
In short: it would take me a whole lot more time to evaluate whether or not to depend on something as trivial as leftpad than to write it myself. I'm pretty confident I can do that in a minute or two and I trust my collaborators to not break it.
