Maybe it's because there's no killer device yet. Or maybe it's because we hate charging yet another gadget. Whatever the reasons, a large number of consumers just aren't sticking with wearable devices--like smart watches and fitness trackers--after they buy them.

A new study from research firm Endeavour Partners says that one-third of American consumers who have owned a wearable product stopped using it within six months. That number goes to 50 percent for activity trackers like the Fitbit, despite the fact that 1 in 10 U.S. adults already owns one.

MORE: Android Wear: Clock Now Ticking for Smartwatch Competitors

The wearables market is still very young, but it's expected to grow by leaps and bounds, reaching $19 billion in sales by 2018. That's according to Juniper Research, which had predicted $1.4 billion in wearable sales for 2013. However, if wearable device owners continue to abandon their gadgets, perhaps the category won't explode like some predict.

You could blame some of the fatigue on clunky first-generation hardware. The original Samsung Galaxy Gear, for example, suffered from a bulky design, short endurance and slow performance. The next wave of devices, including the futuristic-looking Gear Fit, promises to improve on some of those beta-style shortcomings.

Other major players have yet to enter the market. Google made a splash with its Android Wear watch announcement, but those devices won't reach shelves until the summer. What's encouraging about Android Wear-powered watches like the Moto 360 is that they don't look like calculator that's strapped to your wrist. 

Apple is also rumored to be entering the wearable space with an iWatch late this year, which purportedly will feature a curved glass design and the ability to run iOS apps (though they may be of a scaled-down variety). Apple's device is also expected to place a heavy emphasis on fitness.

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Even more nascent is the heads-up display market, spearheaded by Google Glass. That device has yet to go on sale but has already proved polarizing, leading to some businesses banning the first wave of wearers from using it in on their premises.

The key for wearable device makers will be keeping consumers excited long after the purchase. This means they'll have to find ways to keep us motivated and also devise clever ways to keep our smartwatches, trackers and glasses full of juice, perhaps through new wireless charging technologies.