This should probably be required - there is a different mindset and set of restrictions when you're expected to pick up a page. It also forces companies to use on-call judiciously - not every service needs a 5 min SLO.
It’s all over the place. Most of my jobs wouldn’t intentionally contact someone after hours or on weekends unless it was a real emergency or urgency that couldn’t be avoided.
I did work for one company with an executive who liked to work odd hours and demanded responsiveness from everyone. Got so bad that he would regularly be unavailable during the workweek daytime hours but would start tagging people in Slack on Sunday morning or at 9PM. He would threaten to fire people who weren’t responsive enough and I once got threatened for not responding fast enough on vacation. As you might expect, turnover was very high for that company.
More generally there is a problem with people not understanding how communication tools like Slack should be used. I’ve had to teach a lot of non-technical people how to disable push notifications for every message in Slack. They would install the app and start receiving push messages for everything said in all of their channels, then they would think that meant they had to respond to it. You have to set some expectations and communicate what’s expected, otherwise some people will assume every message that appears on their phone is something that needs acknowledgement right away.
Usually about covering shifts.
Basically they paid like $2-3/hr (15-25%) more and fired people who called out twice. Their turnover and shrink was like half of the norm and it was a really successful business.
Low turnover is a big deal in that business. Transient employees pilfer like crazy and fuck up more. You yield a good ROI on shrink with smarter labor. A fucked up preparation or stolen cold cut ham can cost a weeks labor.
There are some true scumbags out there.