Since the introduction of entities, I think this feature might come in handy for users using odk to develop highly powerful functional forms that might outcompete some ERP softwares in some niches.
With that said I believe the xml form might need to be protected as an intellectual property. Also the csv entities may need to be protected from access or malicious modification(as they might contain PII or passwords) even if using usb to access android odk folder on the laptop.
For me one particular case I wish this feature existed is when i was using xml form calculate question to generate a random number as a password to skip some group of questions. This was a time use repeat section of survey. It recorded the task performed during the last 24hrs. Some respondents find this sensitive or much involving and therefore aborted the interview.
I could also not let it optional as the Enumerators are like current flow in electricity, they would opt for an easy path to meet their daily targets 
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So I wanted away to skip these group of questions by entering the immutable form instance specific random generated password. Using the hint generated from the form note i would compute the password and share with the enumerators to proceed with the interview without the time use section. So this acted as a valve to control the number of submissions with time use section missing.
However, some enemerators were cheeky and were able to view the form definitions.
So I concur with Rusti. This is a feature that its time is due.