An iPhone fold could be an iPad when you want/need the bigger screen and iPhone when you want/need pocket ability. Many things that make someone want both devices can be merged into a
single device to use in either mode. THAT is the problem for which a foldable device likes these solves.
- Carry ONE device for both jobs instead of TWO for when you may need "the other one."
- Buy ONE device to scratch both itches instead of buying two.
- Carry less weight around vs. carrying both a tablet and a phone that otherwise are almost the SAME functional device differing mostly by size of screen.
...all tangible "problems" that a foldable (or rollable) screen device readily solves.
There is currently no way to expand the width of an iPhone when you want to do something that works better or is more enjoyable on an iPad screen. (Sans very big pockets) There is no way to put an iPad in your pocket so you have it with you even when you are not actively using it.
Our Appleverse seems so locked in on some kind of concept of "protect our turf" phone form factor that we ridicule this every time, mostly revolving around that line. However, we did the same when Apple told us that 3.5" was the perfect screen size as competitors rolled out phablets... and again when Apple shifted "perfect" to 4". "We" had a dozen or so punches at phablets ranging from stupid/abominations to "pants with bigger pockets" and "one handed use" WHILE Apple did not offer a phablet size phone. When Apple rolled out their phablets, all of that wall of phablet rips- which did include "solution in search of a problem" evaporated, almost overnight... replaced with "shut up and take my money", "best iPhone ever" and soon "how did we ever get by with those puny screen phones?"
Right now, we are in "protect our turf" mode again... ridiculing something different because Apple doesn't offer it yet. However, when the rumors start piling up about an Apple iFold... as we start believing Apple really is going to go there... the collective sentiment will moderate into "wait & see one in person" and "it's starting to kind of grow on me." When Apple takes the stage and introduces one, once again-
as we do EVERY time- it will be "shut up and take my money", "best iPhone ever" and soon "how did we ever get by with those tiny-screen phones?"
Need another example: for YEARS, "we" have ripped the punch hole phone screen in defense of the "iconic", "I love the..." notch. As rumors pile up that Apple is about to go pill & hole, one can already see moderation in what was very passionate hatred(?) of it among some of that crowd. As more rumors pile up, I fully expect more moderation as more come to believe it may really happen. Should Apple take the stage and roll out a pill & hole phone, "shut up and take my money", "best iPhone ever" and soon, "how did we ever get by with that humongous notch eating up so much of the screen?"
This same movie plays out the same EVERY time. Before Apple has something different, we hate it, it's stupid, gimmick, 99% don't need, etc. After Apple goes there it can become the main reason "we" are strongly pushing upgrades now. See NFC payments before Apple Pay, see front facing iSight camera NOT in iPad 1, etc. That list is LONG!
Personally, I use an iPad mini 6 as both principal iPad and Phone (celluar model with buds and a VOIP app). For my purposes, it is a terrific iPad and "iPhone" in ONE box with a much cheaper cost of 5G service. The one glaring advantage of iPhone vs. this to me is the ability to readily pocket iPhone. If I could basically fold this in half to pocket it, it would be- IMO- the perfect dual function mobile device.
Very tangible problem: not as "always with you" mobile (pocketable). Solution: iPad with cellular & Voip app that can fold down to about iPhone Phablet size. Best of both worlds IMO. I'd be first in line to buy that.