I've heard it said that you can just alternate between two UI themes once a week, and every time you switch, the new one will feel prettier, newer, and more exciting than the old one.
This is a natural tendency. The human mind is intrigued by change. That's where fashion comes from, and fads. It gives you a little burst of some chemical, maybe adrenaline (fear of the unknown?), or endorphins (appreciation of the unexpected?), or perhaps some other kind of juice I heard of somewhere but I don't really know what it does.
In tech, this kind of unlimited attraction to the unexpected is the main characteristic of the first phase of the Technology Adoption Lifecycle, the so-called "Innovators."
Source: Wikimedia Commons
Perhaps people are happy to be included in the Innovator category. But Innovation isn't just doing something different for the sake of being different. Real innovation is the willingness to take the risk to do something different, because you know that difference is expensive, but that it will pay off in some way that more conservative sorts will fail to recognize until later.
In fashion, the end goal is to catch people's attention; if you do that, you are innovative. That's why fashion repeats itself every few years: because you can be innovative over and over again with the same ideas, rehashed forever.
In technology, we can hold you to a higher standard. Innovation requires difference, but it also requires a vision of usefulness. Change is expensive. Staying the same is cheap. Make it worth my while. Or if I'm an Innovator, or even an Early Adopter, at least give me a hint about how it's worth my while so I can exploit it while others are too afraid.
Every needless change creates expensive fragmentation. Microsoft ruled their market by being change averse. So did IBM. So did Intel. Even Apple. Whenever they forgot this, they stumbled.
Change aversion works because what makes a platform successful isn't so much the platform as the complementary products. For a phone, that means third-party power adapters, car chargers, headphones with integrated volume controls, alarm clocks with a connector to charge your phone and play your music at the same time. For a PC, it could be something as simple as maintaining the same power supply connector across many years' worth of models, so that anyone who standardizes on your brand will have an ever-growing investment in leftover power supplies plugged in wherever they might want them. For an operating system, it means keeping the same approximate style of UI for a long time, so that apps can learn to optimize for it, and a really great app made two years ago can keep on selling well, perhaps with bugfixes and new features but no need for rewrites, because it still looks like it's perfectly integrated into your OS experience. That sort of consistency allows developers to focus on quality instead of flavour, and produces an overall feeling of well-integratedness. It makes people feel like when they buy your thing, they're paying for quality. And yes, people - moving beyond the innovators into the more profitable market segments of the curve - will definitely pay for quality.
Real design genius lies in the ability to make something look pretty, and with gentle updates to keep it modern looking, without causing huge disruption to your whole ecosystem every couple of years. Following fashion trends, while not caring about disruption, does not require genius at all. All it requires is a factory in a third-world country and some photos of what you want to copy.
Ironically, even app developers mostly fail to recognize just how bad it is for them when a platform changes out from under them unnecessarily. Instead, they get excited by it. Finally, I get to rewrite that UI code I really hated, and while I'm there, I can fix all those interaction bugs I knew we had but could never justify repairing! Because now I have to rewrite it!
Redesigning things to match a moving target of a platform is really comforting, because it's a ready-made strategy for your company. The truth is, you don't have to think about what customers want, or how to make the workflow smoother, or how to eliminate one more click from that common operation, or how to fix that really annoying network bug that only happens 1 in 1000 times. Those bugs are hard; this feels like freedom. We'll just dedicate our team to "refreshing" the UI, again, for another few months, and nobody can complain because it's obviously necessary. And it is, obviously, necessary. Because your platform has screwed you. Your platform changed for no reason, and that's why your users can't have what they really need. They'll get a UI refresh instead.
And although they are less productive, they will love it. Because of endorphins, or sodium, or whatever.
And so you will feel good about yourself in the morning.