If you're going to start lobbing moral accusations on the worthlessness of work that doesn't have any direct moral implications, you have a lot of posts on HN to go through. ;)
First off, don't assume that the two are mutually exclusive. One of the things you learn as an educator in a tough environment is that you need hobbies as an outlet to survive and not become depressed. If you do start to go down that rabbit hole of depression you can have a poor outlook on your and your student's ability to succeed and that is not what an ideal educator needs in order to be successful in the classroom.
Second, I could have used this app over the last year to make me a better teacher. The ability to capture thoughts with words and pictures like this app provides would have been phenomenal for my organization and let me be more effective. I tried other apps and they would not have been as useful as this one would have been so don't discount it because the time was spent working on it instead of other problems that you feel are more deserving of attention.