Maybe it's also because I hate the new skeuomorphic design aesthetic. What's wrong with gloss, gradients, transparency, and attractive animations, or even a bevel or link here and there so we can actually tell something is clickable rather than playing mystery-meat navigation? I swear, everything is going flat-shaded, blocky, ugly, and indistinguishable, all because that's now the new "hip" look.
Skeumorphism - the use of design elements that mimic real life objects with similar functions, is actually the opposite phenomenon from the flat, light-on-pastel design trend. Though I fully agree with you - both of these UI philosophies have been severely overused.
A bit of googling will turn up plenty of articles analyzing the history of the skeuomorphism-versus-flat debate particularly at Apple, which I would argue has been one of the biggest influences in UI design over the last few years. Basically, the loss of skeuomorphism advocates such as Steve Jobs and Scott Forstall led to the pendulum swinging completely in the other direction, and many gimmicky and dated interface elements such as notes apps that look like real paper and a game center that looks like a cheap felt billiard table have been stripped away. But - what to replace it with? Well, everybody wants to stay on top of the latest design trend, and Microsoft and others seem to be migrating to flat designs, so flat it is.
Although you could argue over who copied who, essentially what you have is Microsoft and Apple in a race to see who can flatten their interfaces and strip out any traces of skeuomorphism the fastest. Sure, it looks trendy, but it's reached the point where we are sacrificing usability and accessibility in order to have the most "modern" design. Here's where I have a problem with the whole thing: computer interface elements have been pretty consistent over the last 20+ years or so. Everything behaved as expected and usually acted pretty consistent between operating systems. This is great for users, since they can focus on the task rather than the tools needed to accomplish them, and using the interface becomes second nature. To those who *design* computers rather than *use* them, this is a problem - you want the bling to be noticed. The old way of doing this was to show off your new hardware by making the UI flashy, bright, colorful, inviting - basically by ramping up the skeuomorphic elements to 11.
The problem is, the novelty of this wears off fast, and these interfaces quickly become dated. Now, flat is in, and anything that even remotely resembles skeuomorphism is stripped out. I have a number of problems with the current trend:
1) interface elements are hidden or played down, making them hard to find. Often it's hard to tell if I'm just not looking hard enough for that feature, or if it has been removed altogether.
2) It does away with conventions that have been standard for decades. This means that every time designers go wild designing a new interface, users have to spend time and effort learning a new way to accomplish a task.
3) It's less accessible. Razor thin text is hard for some people to see. Pastel on white and white on pastel text may look "hip" but can incredibly difficult to read. Interface elements that are marginalized can be hard to hunt down if the user doesn't know where to look.
4) It's inconsistent. Some programs hide buttons and scroll bars, some do not. Some use vastly different elements for simple actions such as "close window" so that the user is left guessing at the function of a UI element.
My prediction is that in a few years, "flat" will look as equally dated as skeuomorphism does now.