Now that practically EVERYTHING in life is done on the internet and by use of a cellphone, do schoolchildren even need traditional supplies?

I would hope so.  Some of the most important parts of developing and learning comes from art, learning to be prepared, and responsible for taking your things to and from school. It also teaches organization.  Learning to share physical things, not a picture on a screen,  is crucial. 
Having your fingers get stuck by glue and learning hold hands to be safe. (and for other reasons... 7th grade and Up, Only!)  Having physical things that belong to you and having tools to help you, physically, in life are important.
You need to learn how to use tools to create things, physically.  You need to lean to share those things and help others with your tools if they aren't fortunate enough to have any.
You need to know it is important to have things we all take for granted others provided for us.
A house. A car. Clothes.  All these things are necessities to live as an adult.  They are tools to live a healthy and happy life.  They are the same tools we took to school.  Paper, pencils, a backpack, etc. 
Also, how are you going to be able to make spit wads to spit at Element who tries to teach us  that Big Letters with little numbers attached will make things go...

KABOOM!!

Absolutely! We need things well beyond cellphones and computers.
We need each other and the tools to help us learn to live better, together.

;) :)

This post was edited by Merlin at January 6, 2020 9:59 PM MST

I was shocked to find that they do.  I guess not every activity is immersed in only the internet.  

Kids still need supplies.  I don't know much, but I had several conversations with teachers and they assured me it is a problem where they (the teachers) have to fork out their own money because the school was not supplying needed paper, etc.