When Apple unveiled the Apple Watch in Cupertino last week, the company left a few questions unanswered. Chief among them: Why should consumers want a smartwatch?

Many had expected that Apple might answer that question by unveiling some magical new use case, the long-awaited raison d??tre for watches that extend the phone?s functionality to your wrist. Instead, Apple displayed many of the same features we?ve come to expect in smartwatches: notifications, directions, messaging, and health and fitness tracking, albeit in a much more attractive, usable and appealing interface.

And it essentially punted on the question of the ?killer app? for smartwatches?the feature that will make them indispensable in people?s lives. Instead, wisely, Apple turned that job over to its developers, with the WatchKit development platform.

As it arguably did with the iPad before it and maybe even the smartphone and personal computer before that, Apple did the hard work of building a device with a well-considered and usable interface, and then handed developers that workable canvas on which to draw. So far, the best use for an Android Wear watch is Google Now, and its third-party apps have been limited, at best. But if developers feel they can do more with a platform, history has shown that they will.

The Apple Watch itself is obviously very well thought out. It takes the smart step of repurposing the crown, or the little dial on the side of a watch, as a navigation tool. And design details are everywhere: the coloured dot on the outside of the crown matches whatever band colour you have chosen.

In his presentation, Timothy Cook, Apple?s chief executive, pointed out a few things that might be possible when developers build apps that are deeply integrated into the watch. The one that garnered the most ?oohs? and ?aahs? was a Starwood app that will let you check into a hotel room and just wave your watch to open the door.

Cook said a BMW app could display battery life on an electric vehicle and show you where it?s parked. And although Apple didn?t say much about HomeKit, the company?s platform for connecting and controlling smart-home devices, Cook mentioned a couple of smart-home apps, as well.

When the iPad was introduced, it wasn?t immediately clear what you?d use it for. There were suggestions, of course, that it could be like a bigger smartphone for browsing the web, and that it might be a nicer way to, say, view photos.

As it turned out, need was in the eye of the developers. In time, thanks to apps, the iPad became, variously, a second TV, an e-reader and a full-fledged browser, but also a portable typewriter, a musical instrument and music creation gadget, a video editing console and even occasionally a camera.

The smartphone itself followed a similar path. When it was introduced, it was considered a portable computer that could also make calls. Its cutting-edge features were its multitouch screen and its ability to play music and browse the web.

No single person, most likely, realised it could eventually replace stand-alone digital cameras, kill off the landline, become a navigation device to challenge in-car systems, keep us in constant contact with friends and family, and ultimately become the most important, intimate gadget in many people?s lives.

So it is with the watch.

Sonny Vu, founder and chief executive of Misfit Labs, which makes the Shine fitness tracker, told me once that we probably have no idea, yet, what the perfect reason is for a fitness tracker or a wearable device.

Some developer, somewhere, is even now working on Idea X. Will it make smartwatches as indispensable as the smartphone, or even as well adopted as an expensive slate of glass with no obvious reason for use?

Time, so to speak, will tell.

Molly Wood