I have a hobby-level interest in avoiding pervasive surveillance, and have been thinking about ditching my phone more often. Something like no-cell Tuesdays.
What if I have a family emergency? I don't have a desk phone, but I could pay more attention to my work email.
What if my car breaks down? I could use a payphone, except those don't really exist these days. I could walk to the nearest gas station and ask to use their phone, but they would probably think I was crazy.
The other thing payphones used to have (at least here and there) was an attached phone book with Yellow Pages where I could find a tow company. Lets say I do manage to beg access to a phone, how do I know who to call?
Now that everyone carries all these things in their pocket, other systems for handling these problems have atrophied.