It's also doesn't fit well with modern narratives when they encounter and kill Humbaba. It would confuse the heck out of the audience that they negotiate and offer gifts to Humbaba. Then Humbaba tries to run away and they chase and kill him anyway, and then they piss off the gods for doing it. He's also the guardian of the forest, which today is supposed to be a good guy. It's all so morally untidy.