They did. Those sonic cannons that the military used against the Hulk in his own movie were based on that tech and Hulk smashed them. You can even see the Stark Industries logo on them.

Expecting continuity and logic in movies like this I've always found stupid. Especially when people call a movie bad just for having tiny issues like this. It's why I don't like channels like ScreenJunkies, HISHE, or CinemaSins that much because they feed off of tiny little errors like this. Even if they don't use it as legitimate criticism most of the time I just think it drains the fun out of movies.

Like this is a movie about a rich dude in a huge-ass robot that probably weighs as much as a few elephants and a scientist turned into a green invincible rage beast by gamma radiation and you expect them to bring up a plot point from a movie release years and years ago from the very beginning of the continuity and use it now also depriving them of one of the coolest scenes in the movie. And if you're going to get nitpicky like that maybe there's no more of that tech because Stark stopped making weapons a long time ago and worked to destroy his past work. He probably wanted this thing especially gone because of his harrowing experience with it.

So yeah, nitpicking is obnoxious to me. Not a big fan.