When we say that a particular version of an operating system (OS) is 'stable', we actually mean that its application programming interface (API) and application binary interface (ABI) will not be changed within the lifetime of this particular version of our OS. Granted, that's a programmers' definition, but that's what stability means for any IT professional.
For the ordinary user, 'stable' has an entirely different meaning. For him, this attribute signifies that the OS and all applications installed under it run smoothly and don't segfault. Conservative users valuing this virtue tend to use Debian Stable or Slackware, and they also tend to confuse age with stability.
I was surprised to find the same attitude where I would have least expected it: in a discussion about Manjaro, an Arch-based Linux distribution. Manjaro is currently hyped similar to Ubuntu a decade ago, and is explicitly praised for having an own packaging system (unlike ArchBang, for example). Official Arch packages are held back in a 'testing' repository for an indefinite time (typically a few weeks) until they are deemed to be fit for the 'stable' repository.
Allan McRae has criticized this 'feature' repeatedly, and rightly so. Delaying critical updates to create the impression of a well-tested, 'stable' computing environment is a very cheap marketing trick, but one which seems to work well judging from the comments to Allan's blog entries.