In the vast majority of cases, its not. But in the cases when people want to invent new globally useful abstractions, like bignum, promises, cleaner streams etc - i.e. to reshape the platform - they can't do that. For example, the overhead of adding bluebird as a dependency to every module quickly adds up, and bluebird had to fight with many issues stemming from multiple versions of it communicating with each other.

IMO while this has contributed to the growth of node the ecosystem, it also stifled the growth of node the platform.