(1) Most programs don't have that many direct dependencies, especially smaller dependencies. It's often dependencies of dependencies. In npm, adding just `jes

(1) Most programs don't have that many direct dependencies, especially smaller dependencies. It's often dependencies of dependencies. In npm, adding just `jest` will make your `node_modules` directory explode. (2) if Linus's Law is "given enough eyeballs, all bugs are shallow", then having fewer eyes on a library means more bugs. (3) Oftentimes you think you can replace a dependency with an afternoon of programming, but it turns out, it's not quite as simple as you think. (4) Sometimes you only use a small piece of a library to start with, but over time use more and more. If it's your own code, then you're going to be continuously refactoring, updating, rewriting it. If it's a library, then you can just start using the additional pieces as you need.