> Someone important trying to call can always leave a message

Curiously, it seems to have become a cultural touchstone not to leave a voicemail. I have had to educate people about this. My service is with Verizon, and for what I assume are historical reasons the caller will hear rings on their end even if my phone isn't receiving the call (AT&T does not have this issue). If you don't leave a voicemail, I literally have no way of knowing that you called. Said voicemail can be as simple as "call me".

I'm a physician, and the hospital where I do most of my work has a policy against sending PHI over text (a very reasonable policy). So many nurses are reluctant to text me anything, even when it's just "please call Adam on 3 South".