Node_modules Is a Cancer

I just scanned my home directory and discovered thousands of node_modules directories filling-up my disk. Many of these are in dot config directories but it seems every bit of software these days contains the obligatory node_modules directory chewing-up tens or hundreds of megabytes. With Ruby I have a single .gem directory and Node itself has a global node_modules directory so why this need to re-download half of npm.org every time?