Ian and Peter really nailed it with their comments. For me, the mental complexity of trying to hold a huge API in my head all at once greatly outweighs the cost associated with taking some time to find a well maintained, tested repo that does the exact thing I need really well :) Another great example came to me today: syntax highlighting. The readme on our solution [here](https://github.com/segmentio/highlight) hints at why the decision to break things apart made sense for us. As for both mental complexity and ease of use, I think this is a lot simpler than something more traditional like, for example, highlightjs.
Rather than go to highlightjs's website to download a custom build of the script that doesn't have 22 languages (20 of which you probably don't need), adding it to your asset pipeline, then repeating whenever you need to add a new one, with highlight's plugin approach + a simple package manager and build process like duo, you can easily add and remove each language from your build ad hoc.
Rather than go to highlightjs's website to download a custom build of the script that doesn't have 22 languages (20 of which you probably don't need), adding it to your asset pipeline, then repeating whenever you need to add a new one, with highlight's plugin approach + a simple package manager and build process like duo, you can easily add and remove each language from your build ad hoc.