Planned Obsolescence in Phones
Lets use Apple as an example as they are well known and popular.
To have the latest product is deemed cool on a social and technical level, and the industry encourages this thinking.
Technology is constantly upgraded so that older iPhones (3G etc) are incompatable or problematic with certain apps or the latest larger screen sizes (6S).
In addition, software is updated regularly often with a complete visual redesign. For example when iOS 7 came out, everyone updated their phones for the newest look. People with iPhone 4's found their phones slower and their batteries drained. The iPhone 5 which had recently launched did not experience these problems. Customers looking to fix their phone unsurprisingly found it easier and cheaper to upgrade and repurchase.
There is much debate as to whether Apple were aware when they produced the 4 and 4s, that they were going to release an iOS software that would be too much for the phone to handle.
Plus phone manufacturers often make it impossible to purchase spare parts (iPhone batteries for example) without returning to their store to purchase, keeing all sales within their company.
Apple is just an example here, many manufacturers involve themselves in this practise from phones, cars to coffee makers.
