So if your software needs to run 24 hours and something breaks with your software, how do you avoid being on call?
A developer shouldn't be the first person called, there should be an operations staff but they may have to escalate.
On the other hand, any time that a developer is routinely being called in the middle of the night, there is usually either an issue with the software or the infrastructure not being fault tolerant.
In the UK there are laws you can opt out of being asked to work more than a certain amount of hours. They company should have an out of hours plan but most experienced developers will know very few things get resolved in the middle hours of the night, things need testing, reviewing and sometimes the solution is not simple, it is better like you said to have ops staff that gather data and then pass it on when devs are in fresh, however if you have, say, a big international sale which is happening in another timezone then why not just pay staff as a one off to be around?
A developer shouldn't be the first person called, there should be an operations staff but they may have to escalate.
On the other hand, any time that a developer is routinely being called in the middle of the night, there is usually either an issue with the software or the infrastructure not being fault tolerant.