Every inventor typically thinks this is the easy path to being a millionaire. It is the one thing that will discourage most inventors because they feel that the company will make millions selling their item and it will change the world.

The big companies (or the management in them) are actually adverse to risk. They don't know if your product will sell millions for them. They don't want to risk their jobs and reputation on your product. That is why you mostly see these companies just modify existing products.