I would hazard a guess that a very good photographer with an iPhone X could surpass some of the studio work I’ve seen. As always, being a professional simply means you are getting paid to do something. It does not always mean that you are good at what you do. That being said, I would never pay someone to take pictures with a phone. I have actually heard of “photographers” showing up to take family pictures with a phone. Unacceptable IMO.
The customer gets what he/she pays for. In the end, they're paying for great photos, not equipment rentals.
Apple certainly has paid professional photographers to shoot with iPhones, and a number of major publications have engaged pros to use iPhones for cover shoots and major pictorials (no doubt with Apple's encouragement). There's a fair amount of professional video out there shot with iPhones and iPads - assuming the only definition of "professional" involves payment, those YouTubers are certainly making money
The thing is, professionals use "non-professional" tools all the time. They use the tool that works. Sometimes the only significant difference between pro gear and consumer gear is durability. Other times, pro tools may deliver a broader range of capabilities and controls - if you don't need those extra capabilities, maybe you're wasting your money (or lugging too much weight) by carrying pro hardware. There are also times when pro tools deliver greater degrees of precision ("technical quality"). Again, it's not always necessary. An "adequate" consumer tool in the hands of a skilled pro can deliver far better results than many consumers can deliver with the shiniest pro equipment.
When it comes down to it, when the customer is hiring a pro, the customer feels better when that pro uses recognizably professional tools. On the customer's end, it reinforces their decision to use that professional (say, when an ad agency brings their client to a shoot/recording session). They're paying for the best, after all. On the pro's end, it helps justify the paycheck. "My stuff costs a lot more, so I naturally have to charge a lot more."
I can legitimately call myself a professional photographer, though I'm not a full-time working pro (I was a full-time audio pro for decades). Some of the most personally satisfying, creative shooting I've done over the past few years has been with my iPhones. They've been the right tools for the job (either by capabilities or by simply being the camera I have on hand at all times). I don't make excuses when I show iPhone images. More likely, I'll boast that I was able to take such a good shot with "just" an iPhone. I think it says more about my skills than if I had been shooting with a $5,000-$20,000 bit of pro gear. Still, when I'm on official shoots, the iPhone usually stays in my pocket. People still expect a professional photographer to use a "professional" camera.
As for that last little bit,
I have actually heard of “photographers” showing up to take family pictures with a phone. Unacceptable IMO.
Gotta tell ya, a huge part of taking good candids is that the subjects be relaxed around the camera/photographer. When people spy big, pro gear, they tend to become self-conscious. On the other hand, nobody thinks twice about being captured by an iPhone - it's such a constant of life, people don't make conscious note of it. (Nikon with huge telephoto = paparazzo. iPhone = fan.) So, when a stranger shows up for the party, an iPhone can turn out to be the perfect disguise. Understanding this is as much a part of being a pro as knowing how to compose a shot, how to anticipate action, how to get a competent exposure, or what shots you need in order to properly document the event.
