Less dependencies = less layers of indirection and complexity making feature addition, iteration, testing, and debugging easier and much faster. If you need to change or tweak a function that a dependency usually covers, it's much easier to do if you're dealing with one single codebase (using same style, idioms, build structure, etc...). You don't have to worry about pinning or unpinning dependency versions and keeping track of their security issue, patches, and minor/major bumps.