Now playing: Watch this: Google reveals Galaxy S4 running pure Android

A pure Android Galaxy S4 isn't likely to drive blowout sales, but it could give Samsung and Google a boost in other ways.

Google on Wednesday at its Google I/O developer conference unveiled a special model of Samsung's flagship smartphone that runs a pure version of Android. What that means is the GS4 model won't ship with Samsung's oft-criticized TouchWiz user interface, and the device will receive Android system updates as soon as they're available.

But the device also has some drawbacks. It's pricey -- $649, to be exact -- and is only available through the Google Play store. It also only runs on AT&T and T-Mobile, and it likely won't be promoted by the carriers. In addition, it's unclear whether all features of the mainstream GS4 will translate to the pure Android version.

"For lots of consumers, the initial cost is so high," Gartner analyst Carolina Milanesi said. "They're not doing it for sales."

So why offer it? Google and Samsung likely never expected many mainstream consumers to buy the device. But it could appeal to developers and ultra Android fans who deride custom software interfaces slapped on top of Android. Other handset vendors, like HTC, also offer special developer versions of their devices with an unlocked bootloader, which allows users to install custom ROMs.

For Samsung, the device could mean earlier access to the newest releases of Android, while appeasing other handset makers that don't have the same privilege. Google simply can point out that the relationship is similar to the Nexus program, which always gets preferential treatment. And it's a way for Samsung to play nice with its close software partner, quelling some recent talk of troubles with Google.

The device also allows Samsung to offer a pure Android experience -- to the users who really want it -- without giving up its strong Galaxy branding. In addition, even if some people buy the Google version of the GS4 instead of the regular version, it's still sales for Samsung.

For Google, it allows the company to offer one of the best smartphones on the market with software the way Google envisioned it. Google hasn't had much success selling devices through its store, and most of those products didn't come with the highest-end hardware. The LG Nexus 4, for example, didn't incorporate 4G LTE, despite that the technology was becoming standard in most new devices. The GS4, however, is expected to post blockbuster sales, and Google now can say one of the world's most popular devices comes with a pure Android option.

The device also may buy Google a little time to get the much-rumored and highly anticipated Motorola phone ready. If the online giant wants that device to be successful, it wouldn't make much sense to release a new Nexus phone right before its launch.

So even if sales are low, it might not matter at all to Samsung and Google. They're likely getting exactly what they expected.