With the Macintosh, Apple did indeed follow up on the Lisa quickly, and managed to secure at least a part of the "personal computer for non-techies" market.
In my opinion, the Macintosh differs from Lisa in a number of tricks with which they made it economical: from ~10K USD to ~3K USD
Starting from the removal of the MMU, to the flat-filesystem, whereas between Newtown and iPhone there was basically not enough CPU power, because the StrongARMs of the time were not able to handle the "
native-handwriting"(1) recognition algorithms, which was supposed to be *THE* killer feature.
(there is even an Simpson episode, making fun of it)
The point is that either they are technological reasons for the state of the art of the technology available, which is not enough, or they are cost reasons, that is, there would be the technology to do it, but it would cost so much that it would only be of interest to a few.
I didn't specify the nature of the ":" operator, so either reason works in the equations.
(1) vs user forced to learn "Graphiti", developed by Palm, for PalmOS-devices.
I remember, it took more than two months just to learn and train to write with the stylus in the way Graphiti required, but in the end it was a stretch that made the device economical (300USD (Palm) vs 2000USD (Newtown))