To call a smart-phone a phone is really a misnomer. We need to think of them as computers with internet connections that we carry around in our pockets.
Why is this an important distinction? From a legal perspective, that changes the perspective tremendously. Consider Connie Crosby's Slaw post "Digital Wallets on Their Way" , and the comment on the post musing about privacy and the warrant-less search of cellphones that is being debated in various jurisdictions.
The privacy aspects of a phone that just makes phone calls without retaining any information, and the consideration of whether law enforcement needs a warrant to look at it – are much different than for the devices we have now. Legislators and courts need to consider that looking at a person's phone may be the equivalent of walking into their house and looking at their bank statements, credit card bills, reading material, photo albums, and mail, and while they are there, nosing around on their computer to see all the files, email and whatever else is there including the sites they visit.
Considerering just the phone aspect for the moment, they track and save data on not only what calls you made, to who, and for how long – but also where you were when you made the call.
Other information that might reside on our cell phones include personal and confidential information such as banking information, health information, where we have been and when, and records of communications on various platforms that are meant to be private. Also consider that for many it is not only personal use, but also business use that will contain personal and confidential information of others.
And while you can make phone calls on smartphones, consider the other devices that they replace, and other things that they do:
Digital wallet, GPS, map, tracking device, camera, video camera, email client, social media client, phone directory, calendar, note pad, to do list, grocery list, book reader, magazine reader, newspaper reader, web browser, clock, alarm clock, file storage, dictation device, music player, video player, video game player, radio, video-phone, TV, dictionary, encyclopedia, research assistant, comparison shopper, calculator, wi-fi hot spot, bar code scanner, ephemeris, music composer, video / music editor, cookbook, translator, metronome, flashlight, level, … and the list goes on.