I agree with your thinking and introduce the possibility of an alternative.  Open source software born out of reasons like QuickBooks doing what they do.

Don't be surprised if there's one right now.

And the reason my customer doesn't have an Internet connection is a two word security term "air gap".  I'll bet money that the CSO at Intuit has implemented them and if not - they will be in the news someday when they loose customer data.

Connecting to the Internet is a security choice.  Selecting a book keeping software that understands my security needs is a top priority.