Because: 1) Bluebird is orders of magnitude faster and more memory-efficient than the current V8 native promises. Better native promises performance has been p

Because: 1) Bluebird is orders of magnitude faster and more memory-efficient than the current V8 native promises. Better native promises performance has been promised, but we are still waiting for it. 2) Bluebird is just as much standard-compliant as are the native promises. 3) Bluebird has very useful extensions, which are not (yet?) part of the standard. You are not forced to use them, but they are still very nice to have.