This is the most important question Apple needs to answer in the next iPad

Rumors of a larger 12.9-inch iPad have been circulating for over a year now. But all these rumors about its size, specs and features have yet to touch on one vital question, one that Apple needs to answer whenever it decides to unveil this product:

"What does a larger iPad do that a smaller one can't?"

The iPad has always been about simplicity - it's so easy that infants and toddlers can learn how to use it with little instruction. All iPads feature one big screen and one main button (besides power and volume controls).

Yet, we still don't know if and how the 12.9-inch iPad will function any differently from the 9.7-inch iPad Air and the 7.9-inch iPad mini.

During a conference call with investors in January, CEO Tim Cook said the iPad was a solid business with room for growth, particularly in the workplace. "The real opportunity is to bring mobility into the enterprises and change how people work," Cook said.

Though this seems like a major hint at a distinguishing feature for the larger iPad, no one has any clue how the larger iPad will take advantage of its added real estate to make it more useful for business or productivity.

One would guess Apple will create specially-made apps for this larger iPad, and that's certainly likely. Apple has a partnership with IBM to build a batch of enterprise apps, likely for the iPad, but it's still unclear what those apps will do and how differently they'll function from Apple's current "iWork" apps like Pages, Numbers, and Keynote.

Other rumors suggest the big iPad will come with Apple's new Force Touch technology, to let the iPad access different functions depending on how hard you press the screen, and even support near-field communication (NFC) technology to serve as a receiving terminal for Apple Pay - this would allow the iPad to serve as a cash register or credit card reader, which would be great for small businesses and merchants. But, all of these features are still rumors, and we still have no idea if Apple actually plans to implement any of these technologies.

The hardware will certainly be a major point of interest, but it will all come down to software in the end. If the bigger iPad isn't better than the other iPads at some tasks, it will be tough to see why anyone should buy this product, considering it will be more expensive than its smaller siblings.

If Apple wants to give a 12.9-inch iPad a reason to exist, it will need to sell us on the applications, not just the pretty hardware.