I manage iPads at my company for our electronic medical record system. Can someone explain to me why the older iPad (even iPhone) generations are not compatible with the latest model iOS software? For example, I've spoken and read about too many people with iPad 1st and 2nd generation who said iOS 9 caused major issues with their iPad. I had an iPhone 4S that had major issues following the iOS 8 software update. Our company currently uses iPad's 4th generation and our EMR vendor requires us to update our iOS to be compatible with their application. I just want to get some info so I can better understand why. Thanks for any help!