I agree with Bad_Wolf. It is simply to much work for the developers.
Yes, it would be nice, but don't get your hopes up.
No. It's just movie magic and stupid.
If you want to shoot "harder" at a target, get a bigger gun. If you want to shoot at 2 targets simultaneously, good look making that work.
I would like for them to put it in because I can use a gun with either hand and would like that to be reflected in a couple of the characters I create, but I understand that it simply isn't a very big deal. Using a gun in both hands at the same time though is just plain impractical, and would likely just result in you wasting ammunition.
Ambidextrous simply means your adept at using both your right and left hands fairly equally, not dual wielding guns...which is a bit Hollywoodish.
That said, even though that is a bit unrealistic, it might not be so bad if it came as a perk or trait. Of course it would need to come with drawbacks, like a stiff accuracy penalty for having the ability to fire twice as fast.