"You import someone's changes to a local notebook" <-- there are no existing tools that reliably automate that. (I'm aware of the notebook diff utility in the AuthorTools package, but that's not reliable). There are many tools if you're working solely with plain text.
I hope one day it will be released, either by me or by someone else. :-)
> There are many tools if you're working solely with plain text.
…which means, people choose plain-text due to time preferences: a certain gain in short-term is preferred to uncertainity of the outcome when they build tools for themselves. String-oriented environment is thus preferred not because notebooks' functionality is somehow bounded ultimately.
