Phone call protocol
Way back when phones were stationary, we moved away and towards them. If you were not physically present when a call came in, you missed the call.
Now phones move with us. We do not dial a phone: We call a person with the unspoken assumption that they must answer.
We do not call often now, we message instead. This frees up what calls could be. I like to see calls as a "hello, I'm thinking about you, only answer if you want are present for it".