A single-function book is your window to the world. A phone is the world's window to you.

https://news.ycombinator.com/item?id=48662381#:~:text=A%20single%2Dfunction%20book%20is%20your%20window%20to%20the%20world.%20A%20phone%20is%20the%20world%27s%20window%20to%20you.