Many people are asking why we've stopped supporting the iPhone 3G. It's because Apple has stopped supporting old iOS versions and old iPhones in their most recent version 4.5 of Xcode, which is the tool (the only tool) that engineers use to make iPhone apps.
The iPhone 3G has a special place for me in my heart - it was the first smartphone I bought in January of 2009 and it was the first phone on which we started developing WhatsApp just a month later.
Then as now, however, we must follow Apple's lead on all things related to the iPhone. Their pace of innovation has a price of forced obsolescence.