You know when you’re on a call to someone, mobile to mobile, and the call drops? How often do you ring back, only to find the other person is ringing you back, so you both end up talking to voicemail. Wait a second, though: are they ringing back? You’ve no way to tell. Perhaps they’ve gone into a tunnel or something.
It’s a bit like looking for someone in a supermarket: if they move around looking for you, while you’re walking around looking for them.
Presumably the phone companies would make more money if these dropped calls were automatically resumed.
Until then, we need a protocol. If you initiated the original call, presumably you did so for a reason, even if it was just for a chat. The original recipient’s job should be to wait.
Problem solved. Maybe.