Also, it's an ecosystem feature. If a library or a component of rails (e.g. ActionMailer) wants to process something in a background queue, the choice doesn't have to be between a host of bad options:

  * Forcing a dependency on a particular queue
  * Writing a wrapper for all possible queues
  * Falling back to queue-less behavior in the absence of a detected queue

They just use the Rails queue and it works on whatever real-world queue the user picks. Definitely good infrastructure IMO.