Not really -- some people's only email access is the iPhone. It seems odd to us of course. For me it would work, but not everyone I think.
Businesses started going to email only about 15 years ago for low-wage workers and everything was done over email - hiring, scheduling, etc. I used to get a lot of these emails because people used one of me email accounts to apply for stuff (it was a very short address) so I'd get all of their emails on hiring and scheduling.
The US Government eventually provided free mobile phones and service so that people could work and also use government services. PCs cost more and you'd have to include some kind of broadband access.