I work at my current barn at least 3 days a week and am there all the time, so I know all of the horses well. We've had people come and go. Rarely does someone leave because of us. In fact, I can only think of a couple of people who have left in the last year. One on perfectly good terms and is still a friend of the owners. She just had a better trainer opportunity elsewhere. The other was not perfect. The BOs are very nice and accepted her lie as truth because she had mentioned her situation a few times. It was a white lie and she never paid her 30 day notice.
The only other people who have left have been asked to leave. We never treated their horses differently before they left...mostly because we were glad they were leaving. Why leave them on even worse terms than they already are?