The news went out yesterday morning: Office supply giant Staples, faced with declining retail sales, will have to shrink its physical square footage by 15 percent as part of an overall reorganization plan. What’s to blame for the company’s woes?

“The No. 1 reason for softness in this business is the iPad,” retail analyst Gary Balter told The Wall Street Journal. “Look at how much less we print today.”

The iPad. Along with email and cloud-based data sharing, it’s moving the world away from stacks of paper and everything needed to manage them: filing cabinets, folders, printers, cartridges, binders, highlighters, labels, sticky notes, clips, legal pads. That’s too bad for office supply chains, which are downsizing to adapt to consumer habits. But it’s great news for cities: smaller, more convenience-focused stores will fit better in urban spaces, fleshing out neighborhood corridors rather than forcing people to drive to faraway shopping centers.

It’s just one way the mobile revolution is changing the shape of cities for the better.

The broader big box assault on the urban core—witness multi-story Targets and mixed-use Walmarts popping up in neighborhoods all over the country—has lots of reasons behind it. Primarily, mega-retailers have simply saturated suburban markets, and are looking to tap into America’s resurgent metropolitan wealth. But even if the more diversified companies aren’t as threatened as Staples by the obsolescence of whole product lines, the growth of online shopping allows them to stock only the items that people need to touch and feel before buying, or might need to pick up on the spur of the moment. The resulting smaller boxes can more easily be shoehorned into cities, where Supercenter-sized spaces are nearly impossible to find.