The subplot involving Hulk and Black Widow, also known as Bruce Banner and Natasha Romanoff, saw prominent screen time in 2015’s “Age of Ultron,” which ended unresolved after Hulk flew off into space at the end of the movie.
While the characters shared a brief scene in “Infinity War,” there was no reference to their past in “Endgame” – because there was just too much plot, according to writers Stephen McFeely and Christopher Markus.
"We certainly tried to," McFeely told Empire’s movie podcast. "In ‘Infinity War’ we have scenes — we wrote them, we shot them — of them sort of hashing that out," ‘You’ve been gone, I’ve moved on,’ that kind of stuff.
“It became very clear that if a scene was not on the ‘A plot,’ it could not survive ‘Infinity War,’” he continued. “That thing has to be on rails just to get to the finish line. You couldn’t wrap up loose threads just because you wanted to.”
Markus said it would have felt strange to squeeze in the romantic development to the already 3-hour runtime, in which the team was focused on saving the universe.
“It [would] seem a little odd, in the midst of everyone’s mourning and [Hulk’s] change to a 2,000-pound genius, to go, ‘And they’re dating!’”