I have no words to express how much I hate US culture around on call duty. When I was on call in Europe, in 2 different countries, it was either:

* you're on call but you get paid extra hours for each hour on call. This was enforced by law. You're asking an employee to put in more than the legal 40-ish hours? You pay. Let me tell you that companies only used that when they really cared about being up 24/7.

* your work hours were aligned with on call duty. So yeah, for a week every other month or so you were working 8pm-4am or something like that. Probably awful when you have a family but at least you're not 24h on the clock.

US companies are so freaking entitled when it comes to demanding on call support from their employees.