Comment by kbart

"Every line of code you write is overhead that must be tested and maintained."

The problem is, that modules doesn't solve problems magically. Every dependency should be tested, maintained and kept online as well, by somebody else, whom you have no control of. In turn, you have a bunch of black boxes that can blow up your application anytime. Of course, another extreme of write everything yourself is also bad, so it's a trade-off that must be considered carefully. I've build many systems during my career and one of the biggest nightmare I encounter is managing dependencies.