On call is a symptom of poorly run company. It's a great signal that you should run far away from any place that requires it.
Most software isn't as critical as we think, and the software that is, is expensive enough to have a properly sized staff.
On call exists for the same reason game devs are paid shit and open source exists... Software engineers don't value themselves properly and love giving away free labor.
Plus, we have customers who actually work during the night, be it timezones or specific industries, so we can't just ignore outages outside of our engineers work-times. And if you're selling SLAs to your customers with promised up-times etc. you better be able to detect and fix something ASAP.
Overall I think "On call is a symptom of poorly run company. It's a great signal that you should run far away from any place that requires it." is a bit too harsh of a statement.
I've never worked at a company which had 24/7 staff, I guess that would require international teams.
> If you try to offer 24/7 service and sell SLAs without actually having support people working 24/7 shifts [...] that's the sign of a poorly run company
The reason I almost can't agree with this is, that almost everyone I know who's working in IT Engineering/Administration works in on-call. This includes people working at the federal post, railways, biggest banks, largest grocery stores, national TV/Radio etc. And that's all in Switzerland, so I doubt that these companies are all poorly run.
It's also not really lying to customers, because customers know about on-call. They know that people generally fix stuff during business hours, with on-call people watching out for the systems during non-business hours.
I wonder if it's a cultural difference or something. I rarely hear people complain about on-call. Not many especially like it, but it's considered to be a thing you just have to do. Also, everyone I know gets paid extra for on-call, and it being Switzerland, on-call has lots of rules.
If you're interested, here's a webpage where the government writes about on-call and all of its rules and definitions, https://www.seco.admin.ch/seco/en/home/Arbeit/Arbeitsbedingu...
Hiring, say, minimum 4 people to do nothing but waiting for a page would be incredibly wasteful and probably ineffective as they'd have no idea what to do if something went wrong because they didn't work on the system.