Avengers: Age of Ultron had brought together Natasha Romanoff and Bruce Banner as a couple, but come their reunion in Infinity War, there was nothing addressed about their romance. As it turns out, the writers had tried to continue the story, but they couldn't find a way to make it as relevant as everything else.
Talking to the Empire podcast, co-writer Stephen McFeely explained:
"We certainly tried to [continue the story]… 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.' 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."
If anything, I thought that there was already enough content to establish that the two characters have settled for not being together. After all, Hulk did go missing for two years before he found his way back to Earth—add to that five years post Thanos snap—and you can just kind of assume that the two mutually agreed that a romance couldn't work offscreen.
Personally, I thought that the romance between Hulk and Betty Ross was always worth exploring. Even the Hulkbuster armor's name Veronica is a nod to Hulk's original girl (as in the Betty and Veronica rivalry from the Archie comics). We haven't seen Liv Tyler's Betty since The Incredible Hulk, but with her dad Thunderbolt Ross still a presence in the MCU, what are the odds Betty can make a comeback?
Catch the Hulk and Black Widow in Avengers: Endgame now in theaters.