And yet photographers are able to use various Adobe (or similar) products to do real-time edits/sharing of their work. Most people don't need 100% control over the file-system. As long as the particular type of file they manipulate is available in the app they want to use, an iPad works pretty well.
If they have a single app/app suite that does everything, then sure that's fine (as long as it isn't things like copying a lot of data off an SD card or whatever) - the OS doesn't get involved much.
That isn't a common use case unless someone is paying a ton of money for a single, specialized piece of software that does everything they want, and the iPad only is used for that one thing. Which is a very limited subset of 'work'.
