Memorising peoples phone numbers is about as ridiculous as memorising ipv6 addresses, sure you can do it, but what's the point? You've got a perfectly capable computer in your pocket to remember it for you.
You were involved in an accident and your phone was destroyed. Your doctor asks you who they should call. Now what?
Insurance has my emergency contacts
Could you log in to social media and message someone? Or log into google/apple/yahoo and check your contacts?
No, because my password is in my password manager, and I need my (now destroyed) phone for 2FA.
A battery powered device which is prone to failure / running out of power
What exactly are you going to call them on if it does?
Borrow a phone, use a pay phone with reverse charging if required.
Another people's phones.
If I can get online I can get to my contacts. Its been a non issue for me for 20+ years. I'm not going to optimise for something that's not been an issue for 20 years.