Why is it absurd for hip-fire to be just as accurate as ADS? And just because science-fiction is based on reality doesn't mean everything has to be realistic. That's hardly the case in any popular science-fiction.
Because logic. You are literally aiming down the sight. If that doesn't increase accuracy I don't know what does. When you base something on reality you tend to keep things as logical as possible. Same reason why when you pick up a giant gun you would expect it to do high damage and a tiny one to do low damage.
As for the rest of your comment, I don't see what you don't understand. The strategy not only comes from adding in mechanics but also taking them away at times. This is where the balancing aspect of games come in. Sure you can remove ADS and have perfect accuracy but why stop there? Lets remove vehicles and add in an option for super sprint. Why limit the timings of supers? Give it to us all the time and let us decide when to use/not use it.
You want to be all powerful. That's what I'm getting at here. We can debate this all you want but It's not happening.