Every year in mobile hardware has a theme. In 2018, it was the notch and multiple cameras. We're only two months into 2019, and we already have a clear winner: foldables.

This is a new category of mobile device with a plastic screen that literally folds in the middle: Think of two smartphones stitched together, but with one seamless screen that spans the entirety of the device when it's open.

Foldables arrived with a splash when Samsung announced its new Galaxy Fold last week. Then just this week at Mobile World Congress, Chinese tech giants Huawei and Xiaomi each announced their own versions. The pitch for these devices is obvious: more screen real estate but less space in your pocket or purse. And as the smartphone market starts to feel a little stagnant, some are hailing foldables as the next big thing. The Verge's Vlad Savov said they felt like the future. The Financial Times suggested they will usher in a new era of innovation.

That foldables represent a part of the future feels true. But it also seems clear that, for now, the hype is overblown. Until the companies that own the ecosystem from top to bottom tackle foldables, they will remain an obscure, niche product.

New categories in tech are tricky things. When the iPhone was released, the lack of a physical keyboard and some basic features like copy and paste led some people to dismiss it as a serious contender. Now, tens of millions of people are willing to spend an amount equivalent to the price of a laptop on an iPhone. The new approach won out because it offered customers more.

It's tempting to say the foldable will follow the same path to success. Yet, at least with the current crop of devices, reason for skepticism remains.

First, the price for foldables is out of whack with what they actually offer. The new Galaxy Fold will retail for just under $2,000. The Huawei Mate X is even more expensive, at around $2,600. That is an absurd premium. For that cost, one can get a better, high-end phone and an iPad.

The benefit of a modern smartphone is that it replaces enough things — a camera, a day planner, an MP3 player, and so on — to make it worth the cost. It's tough to see why a foldable device has enough value to justify those crazy prices.

More importantly, though, what new categories of digital devices require is innovation in both hardware and software. In this regard, third-party manufacturers like Samsung and Huawei are hamstrung. Google owns and runs the development of Android, and while these devices are only possible because Google added support for foldable devices to the latest version of its OS, that doesn't make it equivalent to a first-party approach.

Consider the 2-in-1 laptop. It was enabled by Microsoft's decision to integrate touchscreen support first into Windows 8, and then Windows 10. That company's Surface line was created to showcase the very best of such hybrid devices. But fast forward to today and even Microsoft itself refers to its Surface line as the best laptops you can buy. Because Microsoft essentially abandoned the tablet portion of its OS, the hybrid category isn't so much a hybrid as mostly a laptop with some clunky tablet features bolted on. Apple's iPad Pro is simply the inverse, in part because Apple is still figuring out how to create an operating system that actually works for a "professional tablet." Neither company has yet set up the infrastructure for a truly hybrid 2-in-1 device.

That is the problem with foldables right now: Without that top-to-bottom integration, everything is a sideshow. Until Google, Microsoft, or Apple fully invest in an exemplary first-party device with software reimagined from the ground up, foldables will remain niche because, for any new category to work, it requires a fully integrated vertical stack.

Rumors of a foldable device from Microsoft have hovered around for a while, one using a new version of Windows that is customizable to the form. Given Microsoft's abysmal track record in mobile, it's a long shot. But that kind of thinking — a new operating system tailored for a new device — is the only way the foldable might succeed.

For its part, Apple will likely wait to see if the category proves itself before diving in. That means that for now, despite the breathless hype, it's still up to Google or Microsoft to figure out a real alternative. The current devices unfold into an Android tablet — and when was the last time an Android tablet was something anyone really wanted to use?