They needed a “big glove”.

Think about it.

If Tony just made a regular sized glove Thanos wouldn’t have been able to get his fat hands into it, and the threat of Thanos getting the gauntlet wouldn’t have made much sense. They needed to keep the prop as a **big** glove.

And yeah I know it’s nano tech and Tony made it shrink to fit his hand, but Tony also has access to his suits AI and systems to be able to tell it to do that. IRL explanation for Hulk being the one to do it comes down to prop size
Just realized the real reason why Hulk snapped