What's eating the iPad? The former king of the hill doesn't seem to be doing so well nowadays, according to Apple's recent earnings call, and the reason may be the very characteristic that made it so appealing in the first place.

Apple revealed during its second quarter earnings call that iPad sales slumped to 13.3 million units during the second quarter of 2014, more than one million units under analysts' expectations and less than the 14.6 million sold during the second quarter of 2013. The sales figures also represent the second straight quarter of declining iPad sales.

"iPad sales met our expectations, but we realize they didn't meet many of yours," Apple Chief Executive Tim Cook said to investors.

One of the issues at hand is the very nature of a tablet. Tablets are not as portable as smartphones and cannot do the grunt work that a portable computer can, making them a jack of many trades but master of none. Let's face it: The iPad series still lacks a USB port, a severe oversight that consumers tend to swallow rather than accept as OK.

Then there's the growing size of smartphones.

Android phones have long been in the 5-inch display territory, and barring some incredibly poor decision making, Apple should be releasing a 5.5-inch model sometime this year. As tablets, such as the iPad mini, shrink down into 7-inch territory, the visual gains from a tablet begin to diminish. Smartphones are far more useful to most, so it's not too surprising that tablet sales aren't the mother lode they used to be.

"This isn't something that worries us," Cook said in an interview with the Wall Street Journal.

And perhaps Cook has a point. Apple and IBM recently announced a partnership that will bolster the enterprise scope of Apple products. Among those who come out on top? The iPad. Part of the deal includes IBM exclusively selling iPads geared toward enterprise use.

"iPhone and iPad are the best mobile devices in the world and have transformed the way people work with over 98 percent of the Fortune 500 and over 92 percent of the Global 500 using iOS devices in their business today," Apple CEO Tim Cook said in a press release. "For the first time ever we're putting IBM's renowned big data analytics at iOS users' fingertips, which opens up a large market opportunity for Apple. This is a radical step for enterprise and something that only Apple and IBM can deliver."

Enterprise markets are important to mobile device makers because of the fact that more and more businesses are allowing workers to conduct their corporate tasks on their personal devices through what's being called the "Bring Your Own Device" movement.

It's unclear how effective the IBM deal will be, however, given that Apple is already the overwhelming winner in the enterprise market.

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