This is exactly the reason why I keep my mobile as long as possible (years). It is a shame to see all the waste we ship to counties like Ghana and Nigeria and call it recycling.
Now, however, the smart phone I bought last year is struggling to run the latest applications due to it's low CPU speed, if I didn't know how to install my own ROMs (and most people don't) I would be stuck on Android 2.1 and that means I couldn't run a lot of the newer apps. Newer phones have actual useful features being added like HDMI-out, NFC, better battery technology, etc.