Marvel Studios has been known to deviate the events in the Marvel Cinematic Universe from the Comic Book Universe but, in the case of The Incredible Hulk and "Captain America: Civil War," screenwriters decided to follow the comics because having the Hulk around would not have made for a good action movie.
The Incredible Hulk is a popular character but he is too powerful for the "Civil War" storyline and screenwriters Christopher Markus and Stephen McFeely both agreed that it was best to keep him and Thor out of the film.
Do you all remember that time in Marvel's 2012 "The Avengers" film when Hulk not only punched Thor out of the scene but he also smashed Thor's brother Loki around like he was some little ragdoll?
That is precisely the reason why screenwriters decided to stick to The Incredible Hulk's comic book absence and keep him out of the picture in the 2016 "Captain America: Civil War." While all the other heroes struggled with Loki, Hulk showed that he can match even the Gods.
Both Markus and McFeely share the idea that having Thor and Hulk in a battle would create an imbalanced fight. "You put those guys in a fight, it's over quickly. It's like, 'Well, we have the Hulk on our side.' Oh, fine, then" Markus said. "You've got to kind of choose your roster depending on what kind of fight you want to have," he added.
So what else could Marvel do if it was banking on excellent fight scenes?
So far, Hulk and Thor were around to help fight against another god and a super powered artificial intelligence but if powered humans are just fighting against other powered humans and you throw in Hulk on one side, fight scenes would be funny at best but none would be considered worthy of being watched because you already know who's going to win. As for Thor, he isn't even human to begin with so he can just go back to Asgard and rule while humans sort out their own affairs.
Perhaps that is the reason why Hulk is appearing in the 2017 "Thor: Ragnarok" instead.
"Captain America: Civil War" rages into cinemas in May 2016.
