I mean, games always have conceits. I shouldn't theoretically be able to patch-up multiple gunshot wounds with the contents of a basic first-aid kit, but I can and do in video games all the time. This is why it's called a 'game' rather than a 'sim' - there's an implied suspension of disbelief just like with most other forms of media entertainment.
I don't think that's true. A lot of realistic features would be counter to the central appeal of the medium and make not just for a less 'convenient' game, but one that has sacrificed its core appeal for the sake of (poorly) simulating a real-world that we already have access to. To me, the best games are the ones that rejoice in what they are.
The thing is, we've an almost unlimited number of games that have already done or do what you're talking about, so why not experiment with something different? Why not have a more realistic sim based shooter or third person shooter that does some of the things the OP is referring to, that might stand out among an endless sea of arcade shooters? For all we know it might make for a really unique, tense and exciting experience.
Personally I think we need to do away with this notion that a handholding field of view is a must for every game. I use God of War as an example of what being ever so slightly more daring with camera can offer, in that I loved its up close and more intimate camera, and the fact that it demands more from the player in terms of spacial awareness and environmental or enemy management, plus gauging audio cues etc.
I think the idea of not being able to see enemies whilst behind cover in a shooter, and having to instead rely on audio cues, ricochet or impact points, footsteps, peeking, shadows, blind fire, corner shooting, stealth and so on, could be quite exciting.