That is where you're wrong. Here is the profile of a hydrogen company: http://finance.yahoo.com/q/pr?s=HYDG

Here is a profile of a agriculture company: http://finance.yahoo.com/q/pr?s=MON

notice the number of full time employees. the hydrogen company has 85. the agriculture company has 18,800

You can argue that if we started using hydrogen powered cars the industry would grow, but it only takes so many people to watch the tanks - while work on their own - fill up.