How would we know unless they do it? Before iphone was launched someone could have made the same point about Nokia's smartphones. They were heavily updated designs of their massively popular Symbian phones. We simply didn't know what was possible until someone put in the work and innovated and came up with an entirely new design.
We know it because the Airbus 320NEO which is based on a late 80s design, does not have all the cons the 737 has, and was the reason Boeing scrambled to make the 737Max.
For my question the phone-equivalent would be someone asking today in 2024 what is the difference between a Nokia of 2006 and an iPhone of 2024, when only knowing that you can make calls with both of them.
I genuinely didn't know that the modern 737s are so much of a hack to get around regulations and save cost on R&D, and thought they were just good aircraft that were worth iterating on.
I'm sure a few PalmOS owners wondered why they don't make the scroll bars fingerable and add a cell phone ;)
But points to Apple for figuring out you don't need a stylus to write either and you can scroll from anywhere. And for, you know, building a device. I thought of a primitive form of it but it never occured to me to do it.
I've had quite a few non phone PalmOS devices though. I think I'm still keeping a non functional Sony Clie [1] in my nostalgia stash. And maybe a Zire Z22, but I may have thrown that away.