Over the course of the development of those apps the developer have used processe that are only available in later versions of iOS and are intended for phone running specific hardware.
The iPhone 3G is beyond it's support time frame as it's ...... 4 years old?
Currently the lowest supported device is the 3GS and even that is nearing the end of it's support cycle.
As the time moves on so does technology and in order for things to get better, we have to get rid of the old things! 😝
I definitely understand your frustration though and to put it into perspective, many other devices (not made by Apple) are not even supported for a year before the manufactuer moves on and stops sending operating system updates.