The points made by treeleaf64 have been taken for granted, definitely need precise explanation.
I actually prefer thick steel plates, and I bottom out hard on them, so I don't think there's any scientific answer to that. Thick plastic cases actually produce a lower-pitched sound than metal cases ... so depending on whether or not you want something high or low is also just preference. The third part is interesting, and MAYBE useful, but would still come down to preference.
Most technology reaches a point where major innovation is few and far between, it stops being revolutionary and instead evolutionary. This is the point where there is very little left you can add to make it better, and you can't remove anything without giving up something.
I doubt the keyboard technology has reached its peak, there are many questions we didn't dare to properly answer like are the cross-shaped switches best for the feeling. In the 19th century people thought science is finished, the only thing left is to find constants and connect the world with existing theories. Then theory of relativity and quantum physics completely changed the field. As custom keebs are slowly becoming mainstream, when the right manufacturer appears the elitist community will change positively.
How many new designs for an axe do you see? A manual toothbrush? How much has the internal combustion engine changed in the last 100 years? why haven't firearms functionally changed at all since the early 20th century? (soon after the creation of smokeless powder) Hall effect and optical switches are the talk of the town again, but they've been around for decades and had fallen mostly out of use. During the dark ages of the keyboard, the 1990s and 2000s, mechanical keyboards became all but extinct outside of industrial and POS applications. Why is that? Because cheap rubber dome boards are relatively reliable and get the job done just as well as an IBM beam spring that would itself cost much more to manufacture than most people's entire computer setup today. If they go bad, oh well, they are worth nothing, so you toss it and get another one. Why has QWERTY stuck around even longer than the typewriter itself by this point? Because, like rubber domes, it is just good enough. We found something that worked so well that going anywhere else with it became a give or take and not necessarily an objective improvement.
We may have personal preferences towards a given technology, and there will always be limited development one way or another. Without something that doesn't fundamentally improve function, cost, or efficiency, we will continue to have keyboards that are functionally exactly as they are now, as they have been for 40-50+ years. I once read a review from some "journalist" on a laser projection keyboard that proclaimed them to be the downfall of the physical keyboard.
I think a perfect example of this is the smartphone/tablet. People heralded them as the downfall of the traditional laptop and desktop computer. We would all soon be doing everything on a useless, tiny touchscreen, instead of with real peripherals ... on hardware with inferior computing ability. We don't have anything fundamentally better than a physical keyboard, we don't have anything fundamentally better than a physical mouse. I don't think that even AR will get there without better integration of depth perception. We'll always be able to cram more transistors into a larger space than a smaller one, so desktop computers will always be more powerful (with better cooling) than handheld devices. Desktop monitors, with modern resolutions, will always make more sense than tiny phone screens in all applications.
All technology rapidly progresses when new, and
can see a renaissance in at least some ways when a related technology emerges or radically changes. As any technology matures, these things become less and less frequent, because we've spent considerable time and effort on perfecting it. Any improvements (so long as they're even still possible) yield less and less practical gains.
Cross-shaped switches may feel better ... to you, and they may not to the very next person who tries them. A lot more changed than the theory of relativity and quantum physics. In fact, I would say that those things have barely contributed anything in the grand scheme of things. Most of our advancements have been iterative, based on other technologies. In the 19th century we had already gone through centuries of near technological stagnation. It would have surprised me if they hadn't thought that we had reached our apex, because the available technology for research and experimentation was abysmal and had changed little throughout history by that point. It took industrialization and mass production to kick start a wave of technological innovation. Carnegie spread the efficient production of steel around the world. With quality and quantity of available steel increasing, the means of production of other products changed. Things that were not possible with existing materials were suddenly possible. These steel products then helped to shape the future of other technologies, and those technologies in turn shaped the future of more technologies (be it through manufacturing optimization or gradually creating better and better scientific tools in order to discover what we previously could not have). Parts were no longer handmade and custom fit, they could be consistently molded, forged, cut, sanded, milled, etc, by machines. The assembly line further optimized this to the point that we could suddenly quickly mass produce things that would cost a fortune for some artisan to painstakingly produce as a one-of-a-kind just a few decades earlier.
We're back to a period of relative stagnation today. I don't see it changing much any time soon. As new ideas and discoveries emerge (most of which now require technology we could not have even dreamt of 100 years ago), because of the technologies we've already developed, we can more easily and quickly identify and eliminate problems with them, and streamline their development and production, but we need another fundamental change on the scale of industrialization to see something similar again, if ever. Otherwise we're stuck with a sprinkling of mostly potential iterative changes, like battery weight, capacity, efficiency, etc.
