And what happened to iPhone 6 Plus users we also need updates please

Unfortunately there is no way to install further iOS updates on your device, as it is no longer supported. You would need to upgrade to a newer device to enjoy the latest iOS version. Apple typically plans 4 - 6 years of support after each model’s release before rendering them obsolete. After that they release software that outperforms the older hardware. For example, I recently said goodbye to my 6S because the iOS 13 and 14 require too much power to maintain a useful life in that model’s batteries.

Here is a complete list of devices Apple still supports: https://support.apple.com/guide/iphone/supported-iphone-models-iphe3fa5df43/ios

Here is a history of iPhone models and iOS versions they support(ed): https://www.statista.com/chart/5824/ios-iphone-compatibility/

because your hardware was discontinued more than 4 years ago and is not sufficient to run newer iOS