I'm a programmer who spends too much time on the computer. And the problem is not the time I spend but my mindset while I'm on it. I adopt an idleness and unwillingness to do anything off the computer. Worse, just having access to a computer makes me less likely to do other things. Should I read a new book, or go on the computer? If I have a computer next to me, it's simply more comfortable to go on it than to open a book.
A smartphone would do to me what a computer already does. And for those who have the same problem as me, I'd argue that in this case the perspective of someone without a smartphone is less biased than that of someone who does.