One of the biggest issue for Australian ad agencies is they often have to produce collateral and share it with neighbouring nations in the South Pacific.
They are often running older version of things like InDesign meaning the ad agencies have to open/backsave in older versions to have the files compatible.
Not really and issue with Illustrator or Photoshop as the file format does not change, but it's a show stopper when working across regions using InDesign!
Exporting to IDML (kind of like a template file) is really not a viable solution as when the resulting file is opened, it's a brand new document that needs to be saved.
As per a lot of things, if you are working internally, not a massive deal which version of apps you use, it's when you need to collaborate with a range of companies that the app versions become a real challenge.