The invention of the small, handheld camera turned street photography on its head. Urban photographers had always shot on the streets, of course. The new technology made realistic, gritty, candid street photography possible — and that redefined the very concept of photography on the street.
Smartphone cameras have become the tool of choice for a lot of street photographers. They're small, quiet, inconspicuous — and equally important, they're almost always at hand. After all, it's been said (by the sorts of people who say these things) that the best camera is the one you have with you.