On an iPhone, what you capture is what you get. You can zoom in and out and see how it’s going to appear on social networks.
With a handheld camera what you capture may not be what you get. The only way to find out is to put it on the computer screen.
There’s no question DSLR cameras are superior to an iPhone. Just try to conduct a jewelry shoot with both devices and compare results. The iPhone photos are close, but no cigar.
But the portability of an iPhone, its pocket size, its computer capabilities, its touch screen, and retina specs, match the immediacy of our real-time world. It shows you what the world looks like and how it is with no delay.
The two cameras coexist, just as the Vinyl player, CD player, and tape player, MP3 Player, coexist with mobile streaming. Everyone has their preference.
Your device selection comes down to choice and situation. Just don’t spend so much time waiting for the perfect setup that you miss the shot completely.