Not all that often, but I don't think that's the point, really. We all have lots of tools and facilities that we don't need or choose to use all that often, but that doesn't mean that we don't need them sometimes - and also value having them available in case we do need them, even if that doesn't occur very frequently.
Our lawnmower and hedge trimmers spend 99% of their time in our shed; but that doesn't mean that we don't need them! How many people carry paracetamol in their handbags, even those who don't frequently suffer from headaches; or a spare key for a family member's house, in the very rare event that they need to access it in an emergency?
They often give them very little notice of things that they need for the next day - so if he could message me at breaktime, I could pick items up from the shops/arrange them at home during the day (I WFH, very flexibly). Without the phone, it's another task to have to cram into the evening - and especially annoying if I've been to the shops that day already and find that I needed one more small item. We're both human, so he might have known a day or two before and forgotten to tell me; or he did tell me and it slipped my mind.
It's also for travel plans and when after-school clubs are cancelled. Interestingly, they went on a school trip shortly before they broke up, and they were all told that they MUST bring a phone with them - one of these dangerous things that teenagers should never use - so they could let parents know if the minibus was caught in traffic and they would be late back... which indeed it was, by almost an hour.
I think it's daft to ask why people should want/need to use modern everyday things when they don't strictly need to. A few generations back, people managed perfectly well with a cold privy at the bottom of the garden, or even just a bucket, and with a tin bath in the living room. Would YOU be happy to be told that you don't need the standard indoor fixed facilities that we have now, and so you aren't allowed to use them?
Yes, we all managed fine at school without mobile phones and the internet... because they didn't exist... but now they do exist, and are a normal part of routine life. You and I are both on the internet now, talking about something that we don't actually need to be discussing at all - and which our grandparents' generation would never have done (and yet still managed to survive overall to a decent old age). How would you like it if you were told that you couldn't call or message your DH from work about anything during your break - because "you should have spoken to him before you left" and/or "you'll see him again this evening" - just in case your using a modern communications tool for a minute or two risks you getting addicted to and doing stupid things with it?
It's not about their safety and comfort being at huge risk; it's just making use of the standard tools that are available in modern life, and not harking back to a time before we had as many options. The pupils at our DS's school have now been issued with paper 'planners', for them to track everything in the old-fashioned way. Previously, the school used an app that students and parents could easily access - one which could be dynamically updated centrally and didn't require 100s of people to waste time writing down the exact same information, and then crossing it out and constantly revising when it went out of date or plans were changed.
It reminds me of the tasks on The Apprentice, where they're given difficult challenges and not allowed to use phones, except for calling people. Those tasks would be very simple if they could access the internet - just like every other serious businessperson will be doing now without a moment's thought.