Google's (NASDAQ:GOOG) (NASDAQ:GOOGL) Android completely dominates the market for smartphones: Last quarter, nearly 85% of the handsets sold globally were powered by some version of Google's mobile operating system.

Given Android's popularity, it seems reasonable to expect that Google's answer for wearables -- Android Wear -- will eventually achieve similar levels of success. Paired with an Android-powered smartphone, Android Wear watches provide their users with updates and notifications, and offer a degree of fitness tracking.

But Android Wear faces a major issue, one that Android itself never had to contend with. Although most of Google's hardware partners are on board, the two largest may be working to undermine it.

Samsung pushes Tizen
Of the six smartwatches Samsung (NASDAQOTH:SSNLF) has announced or released, five run one of its proprietary operating systems. Samsung hasn't shied away from Google's Android Wear completely -- it released the Android Wear-powered Gear Live in the summer -- but seems far more interested in pursuing its own proprietary operating systems than it does in helping Google build a wearable ecosystem of its own.

The upcoming Gear S, for example, will be Samsung's flagship smartwatch when it debuts later this year. Like the Gear 2 and Galaxy Gear that preceeded it, it will run on Samsung's own Tizen operating system -- not Google's Android Wear.

Samsung's interest in Tizen has long been a source of speculation, with Samsung executives occasionally promising to release a Tizen-powered handset at some point in the future, only to later delay the phone. With Android's market share dominance, attracting the developer support required to build a new ecosystem may simply be too difficult.

But watches are an entirely new form factor; one that Samsung -- as the first-mover in the space -- could use to establish its own ecosystem. Its reliance on Google's software was at first advantageous (its earnings skyrocketed in 2011 and 2012) but has proven to be troublesome. Earlier this month, Samsung said its profits would decline by as much as 60% in the third quarter.

Samsung's management may realize that by adopting Android Wear -- an open-source solution that Google will freely give to other manufacturers -- it will eventually face the same issue in wearables it's currently struggling with in phones.

LG with webOS?
Samsung's Korean rival LG (NASDAQOTH:LGEAF) may have reached a similar conclusion. Although it hasn't announced a single product, earlier this month, The Verge spotted a special page on LG's website advertising webOS for smartwatches.

webOS is the mobile operating system developed by Palm to compete with Google's Android and Apple's iOS. Hewlett-Packard acquired it in 2010 with the purchase of Palm, but soon abandoned it, eventually selling it to LG in 2013. At the time, LG (an established Android OEM) said it planned to use the operating system for its smart TVs -- not its mobile devices.

But repurposing webOS for a line of wearable gadgets wouldn't be outside the realm of possibility, and with Samsung's Android-related profits eroding, it may be a tempting option. Until LG formally unveils a webOS-powered watch, it remains speculation (LG has since removed the page from its site) but it certainly wouldn't be shocking.

LG and Samsung are among Google's largest partners
If LG does abandon its Android Wear efforts, and shift its focus to webOS, it could create a challenging environment for Google's wearable operating system. Although there are dozens of Android OEMs, Samsung and LG are among the largest and most important. Combined, the two firms have manufactured nearly seven out of every 10 Android handsets currently in use. Without their continued support, Google may have a difficult time driving Android Wear adoption.

Sam Mattera has no position in any stocks mentioned. The Motley Fool recommends Apple, Google (A shares), and Google (C shares). The Motley Fool owns shares of Apple, Google (A shares), and Google (C shares). Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.