Purpose is easy:
consumer utility, 2 distinct devices- Phone + Tablet- that largely do the very same things (running the
same apps) in
ONE package. Consumers like utility. Recall Jobs' original pitch for iPhone: "a mobile phone, an iPod and an internet communicator." At the time, most of us had all 3 of those as distinct devices, so how did we see a purpose that an iPhone could serve by merging those 3 things into
one package?
The phone is beloved- towards god-of-tech status. I think many of us struggle with any concept that threatens a big tangible change to the form factor. For example, see 10 threads in the last month towards freaking out about rumored camera module platform on back.
So recast the concept from altering "the precious" at all. How would we feel about an iPad that can fold down to be pocketable and that also runs the Apple iPhone app so it can double as a phone too? We seem to have less "the precious" attachment to iPads so the imagination of significant change can have more mental leeway.
The thing here is that both phone and tablet run the same apps. Both are in similar cases made of similar materials. Both have almost identical tech guts inside. The one big physical difference between the two is screen size. So when we argue for 2 distinct products, we're arguing for carrying around 2 very similar things when a good fold or roll design could merge those 2 into one product to carry around: small & pocketable when that matters... bigger, more useful screen when that matters. Reduce the amount of aluminum and batteries and duplicate tech (and tech weight) we carry while still being able to do everything we do on the 2 device types.
"a mobile phone, an iPod and an internet communicator."
"an iPhone and an iPad, as a single product."
Like all rumored new things, I suspect the apprehension and mental resistance only persists until Apple actually rolls one out. Once Apple launches their cut at the concept, we'll suddenly see plenty of purpose... plenty of problems solved by it... etc. Right now- while there is no such thing for sale from Apple- we cast it like we cast phablets while Apple still clung to 3.5" and then 4" as "perfect" screen sizes... or NFC (pay by phone) while that was only a feature on Android phones. Before both of those, it was wall of disgust/contempt. At launch, it was "how did we ever get by with those puny screens?" and calls to boycott stores that wouldn't accept Apple Pay. What changed? Apple did not have it for sale... and then they did. Many of "our" (often very passionate) opinions seem to fluidly adjust- even flip flop- to that specific catalyst.