One of the major pains in the butt for a teacher is getting students set up on a learning web app. Either you spend a bunch of your own time making an account for each student (which is time you could spend doing something more important) or you spend a bunch of class time having students sign up for the accounts during your teaching period (which is time you and they could spend doing something more important).

If a web app had a secure API to include all of my class lists automatically, I'd be much more likely to use it.