"Don't ask to ask, just ask" is great in general, but if I tell someone this, I'm not trying to schedule a single call. It's more asking for permission to call whenever. Depending on who you and your friends are, it can be necessary to give this heads-up at least once so that, as another user put it, they don't get a panic attack from an unexpected phone call. As an older Gen Z, it feels like no one my age really calls each other out-of-the-blue, and you need something like this to establish it.
I realize there are generational differences but I still default to the assumption that calling people whenever (outside of 10PM-7AM for non-emergencies) is fine, unless someone specifically tells me otherwise
No, I don't need something like that to establish anything. My friends are relatively sane it appears. Neither do I expect such a behaviour from anyone. I have a phone, feature of that is you can call me. Complaining about that is weird. If you don't want calls, turn the thing off... But yeah, I realize in other parts of the world, there seem to be different "rules". However, still very weird to me.