They don't, but they're actually not bad analogues for the computing experience we had a couple decades ago. The original 128K Mac (https://en.wikipedia.org/wiki/Macintosh_128K) had a 9" display, after all -- not that much smaller than the display you get on an iPad Air. I bet someone who learned how to develop great UIs on those Macs would be right at home doing the same on a smartphone or tablet.