My kids are 19 and 17 and they both have their phones on vibrate so I am aware of this habit, but until The Guardian put this article out I did realize how big this habit is.

A survey has found only a fraction of 16- to 24-year-olds think phone calls are remotely important - so they’ve put their phones on vibrate
…
Well, actually, loud ringtones are over. A survey by the tech analyst Sensor Tower has shown that the number of ringtone downloads slumped by almost a quarter in the UK between 2016 and 2020 – from 4.6m to 3.7m.

The data shows less ring tones. And also part of the vibrate is hiding the amount of time they r being contacted.

Analysts also said teenagers prefer to have their phone on vibrate or get messages and calls via their smartwatches or Fitbits, so their parents – or their teachers – don’t know what’s going on.

Who remembers phone numbers any more? Remember when you had to dial phone numbers. Now you tell your phone who to dial or you use another app that has your contacts in it.

What seems to be coming soon is a time when you will get a phone with no phone number. You will have a data connection. Are Telcos ready for that? How much of their business is built on the regulatory issues of phone numbers?

And some of the earliest adopters of phones without phone numbers are the Gen Z and younger.