Lots of reasons to do this and I'm sure it's possible for some, but modern life it tough without a cell phone (many mentioned it already, but banking, passwords, 2fa blah blah blah).

I think the mistake many make is switching to a flip phone with basic sms and cell calls - all unencrypted and antiquated.

I think the real answer is unfortunately the one that requires the most work. Self discipline and balance. To help with that is the long process of minimizing apps and services you use, turning notifications off, and hardest of all - breaking the addiction.