It can be hard to predict sales numbers of gadgets and mobile phones, sometimes a handset can take off and become much more popular than expected. It is clear why some phones are more popular than other, the user interface on the iPhone for instance has made it very popular even (or perhaps especially) with the less technically minded consumer.
Recently a lot of very cheap handsets have become surprisingly popular. The rise of the Smart Phone has meant that most of us have mobile which are capable of web browsing, high quality photos and easy email integration. These phones have become fairly cheap on pay monthly contracts so why are people buying cheap handsets all of a sudden? There have always been people who only want a very basic mobile to make occasional calls but what explains the big rise in sales we have recently seen?
The key is that a large proportion of those buying the bargain handsets also own a fancy Smart Phone as well. These handsets are being used as a cheap back up in situations where the user's main handset has either gone AWOL or is is danger of being damaged. The prevalence of free SIM cards and SIM only deals means that a temporary phone is cheap and easy to set up.
Those going on a night out or even a day out (mountain biking etc) can take a cheap handset with them rather than risking breaking their main mobile phone. The back up can contain their main SIM card or a pay as you go one with a bit of credit on it. If the second handset gets damaged you just take out the SIM card and ditch the casing. Many of us already have an old handset lying around which saves the £20 or so needed for a new one.