Exactly. It makes the Hulk look way too easily defeated. I've said this before, the general audience (i.e., the majority of the people that see the film) aren't going to delineate the fine differences between steel and vibranium-tipped (or even Adamantium) arrows, all they're going to see is that a bow & arrow just took out the incredible Hulk. For years, you'll hear things like, "Who cares if he can lift a tank, all I need is my cousin's crossbow and I can take down the Hulk," or "Geez, if an arrow can do that to him, imagine what a shotgun or tank-fire can do to him!"
If I have to watch an arrow stop the Hulk, I would much rather it be a gas pellet that breaks on contact than something actually piercing his skin.
Exactly! Thank you!