I'm gonna hit this from the students side a bit as I've left a few schools myself.
First school I left because it 'hurt' to be there. Physically. Taking a medicine ball full impact in the chest for 20 minutes on my first day did nothing to motivate me to return. Neither did the 20 minutes on the torture rack either.
Second school I left because of a number of things.
I wasn't getting what I thought I should be getting out of the classes. (Partially my fault as I was cronically tired then).
I also felt their warmups weren't safe as firing full force snap kicks into the air did a number on my knees and hips.
Another school I left as I didn't feel the instructor paid enough attention to each students individual needs and that I didn't have the instructors confidence. (IE I was taught because I was a friend, not because he believed in me).
I've trained at an easy half dozen schools. Some just weren't 'my path'. Some were excellent schools with great folks, but just not 'for me'. Others, well....they weren't so good.
I've left due to money, illness, being too busy professionally, no motivation, etc.
It really varies.
For me, I know what I want. The question is, do I settle for less to do 'something', or do I wait until I find it and then run with it?
I've been out now 9 months due to my back and neck. It's very frustrating. I want to get back on the matts, but I like a more intense workout than just playing 'patty cake'. I can't risk taking certain damage. That whole I like to walk and turn my head thing.

I hang out at the camps, I want to bang and roll, but, everytime I think it's safe, something has hapened (like the last week losing feeling in both arms due to neck and shoulder damage) to make me wait a little more.
I think when instructors loose students, when they can't keep students they need to take the blinders off and really look at how they run things. They need to stop the 'well they just werent dedicated' crap. I know several dedicated students who walked away from years of training and either quit or went elsewhere because their needs weren't being met.
In the end, it's a business.
If you don't meet your customers needs, you -will- lose them.
That doesn't require going broke, babying, mcdojoing or coddling either.
It just requires good customer service and a true dedication to really training your students.
peace y'all.
