I agree, but the social norm (for a lot of young people) is not to call spontaneously - at all, ever. Giving people a heads up helps, and then consistently following through, is a step that helps make it happen.
I once dated someone who “didn’t just leave the house for any old outing” and it became exhausting trying to figure out the protocol for what qualified as a worthwhile outing. It was easier to just dump the person instead of playing this little “no you’re holding it wrong” game of comms.
I mean, people are busy and schedules don't always align. Seems like the onus is on you if you expect another friend to answer whenever you feel like calling. Even with my parents we will check with each other via text before we call (being on a time zone difference doesn't help)