I believe it prevents people from accumulating on old versions. Upgrading version becomes a routine thing. Windows XP is an example of what you get with longer release cycles. XP was out so long people began to rely on it in a big way and upgrading becomes a laborious process.
OS X doesn't have that issue, I suspect in part because they are have a more rapid release cycle.
OS X doesn't have that issue, I suspect in part because they are have a more rapid release cycle.