[chillfox]

There isn't a clearly marked line to cross. It's more of a fuzzy wide wiggly line.

But in general something is essential when it is required to participate/function/exist/live/thrive meaningfully in society. These days lots of governments require that you have a smart phone to check in when you go somewhere or to show a digital vaccine certificate. Before that some big social media platforms (which is a big part of society) was either exclusive to mobile or designed to work best on mobile. Some services requires using a mobile app to interact with said service (account management). My current bank is mobile only as an example.