Why does Apple care so much about SIM cards anyway?

Comparison of SIM card sizes by Giesecke & Devrient

Apple(s AAPL) has reportedly offered its design for itsy bitsy SIM cards — known officially as nano-SIM — to other mobile device makers that are part of the ETSI (European Telecommunications Standards Institute) without asking them to pay for it. There’s probably more to it than a sudden spirit of generosity. Apple loves to control the entire experience of its products, and when it comes to the iPhone and now iPad, the biggest uncontrollable element is a customer’s wireless carrier. And having a say in the SIM card, in theory, pushes Apple closer to the long-term goal of controlling every aspect of its mobile devices.

This has bubbled up in the news because of an impending hearing to decide between Apple’s proposal for the design of nano-SIM cards and those of Nokia(s NOK), Motorola(s MMI) and RIM(s RIMM) before the European telecom standards organization later this week, as the Financial Times reported last week.

Why does Apple care about SIM card design at all? Its interest in smaller SIM cards is certainly related to design and usability — a SIM card that’s 60 percent smaller than the current micro-SIM can mean a smaller, slimmer smartphone. And in a power-hungry device like an iPad, the space leftover from a smaller SIM could go to larger batteries or other components.

But there’s more in it for Apple. If it’s able to control the SIM card in phones, it holds more sway over the subscriber. My colleague Stacey Higginbotham has covered this extensively, and was first with evidence that Apple is aiming to cut out the carriers eventually with even tinier embeddable SIM cards made by Gemalto. If they succeed in embedding these cards, iPhone or iPad buyers could buy the device direct from Apple and simultaneously choose the carrier they want to use, and Apple could activate service right at the point of purchase. It also means easier roaming on other networks.

Yes, carriers would have to allow Apple devices to operate on their networks, so Apple has to have support from some of them to pull this off. And that doesn’t seem to be happening in the immediate future.

Nano-SIM cards aren’t the same thing as tiny, embeddable SIM cards. The line from a situation where every major personal cellular device uses the same small SIM card to Apple gaining control of the carrier relationships with its own customers isn’t direct. But you can see how such a strategy to control what SIM cards are used could consolidate power and pull within the industry in favor of Apple. That could come in handy eventually.