[SmellyGeekBoy]

Before email there were phones, and from speaking to older friends in manufacturing it was pretty common for people to be called at all hours of the day and night to fix critical machinery (on the phone or to attend site in person) whether officially "on call" or not.

This is not a new phenomenon.

Edit: Just wanted to add that I'm not trying to justify this behaviour. It was wrong to intrude into people's personal lives and expect unpaid work then and it's wrong now.