The reason you, "have never found a reason to create a module or package", may just be due to your programming style. If you're used to procedural programming, abstraction may not seem like the right choice. You're probably used to creating subroutines...it's just that you don't pull them outside of your scripts. I like shotgunefx's comment, "If many of your scripts that use that code and you find a problem in that code, it much easier to update the module then patch a bunch of scripts."
If you are going to reuse your code even once, you may want to consider making a module out of it. Why recreate it...again, even once.