Why Is Enterprise IT Continually Reorganizing?

It's become an obligatory part of most enterprise IT conversations I have -- what's the latest org structure?

I joke that most enterprise IT shops are always in one of three states: (1) in the middle of a reorg, (2) getting over the last reorg, and (3) preparing for the next big reorganization.

I have been unable to find any useful industry data to confirm my impression that many larger IT shops appear to be in an almost-perpetual state of reorganization and realignment. Much more so it seems than other corporate functions: sales, marketing, finance, HR, etc.

Which brings up the obvious question -- why is this?

And what does it imply for enterprise IT strategy in general?