I tend to see it from the opposite perspective. Physical looking buttons, borders, and always-visible controls were designs born from rigorous user testing in t

I tend to see it from the opposite perspective. Physical looking buttons, borders, and always-visible controls were designs born from rigorous user testing in the 1980s and early 1990s. The push to flat design that really picked up steam around a decade ago did not have, as far as I can tell, the same level of testing, and was promoted largely by programmers who wanted designs that were easier to implement. Platform developers were incentivized to go flat because it lowered the cost of development and development time if developers were using fewer, simpler custom assets. At this time, both Apple and Google were bragging about how many apps were on their stores, and how fast they were growing, and neither wanted to fall behind the other. But admittedly, my perspective was that of a third-party developer. I have no direct knowledge of why Microsoft, Google, and Apple all embraced this trend, and I have only anecdotal evidence that it made things more difficult for novice users. There could be a treasure trove of research showing that flat is better, but I have never seen it presented.