Power
Companies rely on you and your expertise to tell them the best or most efficient way to design the machines or processes that will produce their goods. So, in that respect, you have a bit of power. You've "got the goods," as it were.
However, you're working for those companies; while they're asking for your opinion, they're not required to listen, nor to follow your advice. If they disregard everything you say, you can feel free to tell them to take a long walk off a short pier, but they aren't likely to take that advice either.