Actually most of those businesses have 2 pay structures. What you get paid to be on call, and what you get paid doing the work. I doubt these folks are the problem because it’s long been built into their structure. People know when they’re on call, it’s scheduled. It’s the more office oriented work where you get a call and asked to reply to an email hours after your work day is done.
When I did bookkeeping for small businesses, I SOMETIMES got calls away from WORK————— BUT NO ONE EVER ABUSED it.