But the fact that customers have spoken sort of plays into what I'm saying. Maybe a certain number of the Pro owners felt they had to choose the Pro, because right now it's all or nothing when it comes to the extra lenses, so they chose all (Pro instead of the Air). Perhaps some of them chose the Pro reluctantly due to the size/weight, and if they were given a third option--to bring a full camera only when it suits them--perhaps they would have chosen it. As far as I know, there's no way to know how big or small of a group that is, so this is all conjecture.
But it seems like there should at least be a small group. It's kind of like portable batteries. Imagine for some reason the market for portable batteries was dead, and your phone battery is all there is (and wall/car charging on the go wasn't a reliable option either). How many more people would get the largest phone with the biggest battery just in case, even if most of the time they don't need that much battery? The option of a portable battery allows some people to get the smaller phone that better suits them most of the time, because they know they can bring a battery those infrequent times they need it. A compact dedicated camera could do the same. Many people are fine carrying portable batteries when needed--a camera would be about the same size, so they should be just as willing to carry it. But not if it's DSLR-sized. Just like almost no one would be willing to carry a battery the size of a DSLR, only extreme users would carry DSLR cameras, even occasionally. DSLRs are best and will always be, but again that gap has gotten small enough that for the increase in size (and probably cost? haven't looked at prices), DSLRs have too diminishing of returns for most people--most of whom are ok with ML photos.
The compact camera market is dead. But the premise of my post isn't that Apple should get into that dead market, it's that the market may start to resurrect in the near future if the smartphone road forks. One road would continue the path of phones getting bigger and heavier and more capable--the other road would split off into two devices that specialize but are integrated.
If consumers were willing to carry a separate camera, then the compact camera market wouldn't be dead! Most people don't want to carry a separate device, just for photos.
How can you compare a battery bank with camera? I can buy a Xiaomi 20,000 mAh bank for under $20. That's throwaway money so I can buy a few spares. My family and friends can all use them. An Apple camera, probably at least $1,000 or $1,500 is a very intentional, single use purchase.
Expand your view beyond just Apple iPhone and it will become obvious. Huawei, Oppo, Vivo, Xiaomi, Samsung have tried it all, tri-fold, bi-fold, large, small, flips, etc. Consumers keep returning for the largest, most capable devices. There's no fork in the road where consumers prefer separate devices, at least not in the foreseeable future.