I've been what I considered to be a very good employer - treated my staff generously, improved leave and pay, was very flexible.
It was all very selfishly motivated, I assure you. I don't believe in treating people badly, but I was also tired of working with a bunch of miserable cunts, and wanted a nice, productive working environment. So I read up and followed all the research to improve things. The changes worked. Everyone was happier, richer and with more time.
I expected them to show up and exhibit the skills I paid them for, and to merrily fuck off at the end of the day. I didn't care if someone left, it was an opportunity to hire a slightly different skillset.
(For what it's worth, I found that staff who never switched off performed the worst - their perceived indispensability was actually just being controlling, and their lack of perspective made them excessively emotional rather than pragmatic or rational in their work decisions.)
Anyone who expects more of their staff is both stupid and exploitative.
People are a resource you hire in for a rate. And that rate is for a set list of T&Cs.