You're hearing this less and less for technological reasons, but we should be hearing this less and less for creative reasons.
In 2009, when this book came out, shooting an entire project on just your iPhone was a radical idea. Now, it's common.
What's the next big thing to become common?
I'm writing a book on a phone.
I took these photos on an iPhone, at dusk, in a thunderstorm.
I'm not supposed to be able to do that.
I can't wait to figure out what I can do next using the least of equipment. The less that gets between my brain and end product the better.