I'll grant that -- but it's also a to-do list, which is pretty much the simplest possible application. It's a common "hello world" for GUI toolkits, and it's the first use case in the org-mode tutorial.

Is there any software more sophisticated than 'a 3x5 card with a pencil' which uses this user interface paradigm? I think any paradigm, no matter how confusing or clumsy, is sufficient for that case.