The New York Times Magazine asked a terrific question this weekend. And provided an even better answer in the form of a long feature story. Tremendous article; well worth a full read.
But if you're pressed for time, the best paragraph explains why mobiles are different in developing countries than in the West.
"...forget for a moment about your own love-hate relationship with your cellphone, or iPhone, or BlackBerry. Something that’s mostly a convenience booster for those of us with a full complement of technology at our disposal — land-lines, Internet connections, TVs, cars — can be a life-saver to someone with fewer ways to access information. A “just in time” moment afforded by a cellphone looks a lot different to a mother in Uganda who needs to carry a child with malaria three hours to visit the nearest doctor but who would like to know first whether that doctor is even in town. It looks different, too, to the rural Ugandan doctor who, faced with an emergency, is able to request information via text message from a hospital in Kampala... There’s the live-in housekeeper in China who was more or less an indentured servant until she got a cellphone so that new customers could call and book her services. Or the porter who spent his days hanging around outside of department stores and construction sites hoping to be hired to carry other people’s loads but now, with a cellphone, can go only where the jobs are. Having a call-back number, Chipchase likes to say, is having a fixed identity point, which, inside of populations that are constantly on the move — displaced by war, floods, drought or faltering economies — can be immensely valuable both as a means of keeping in touch with home communities and as a business tool. Over several years, his research team has spoken to rickshaw drivers, prostitutes, shopkeepers, day laborers and farmers, and all of them say more or less the same thing: their income gets a big boost when they have access to a cellphone."