Storage and transport of H2 is a big deal because of the unique properties (very low transition temp/very high pressure for liquid). That generally means for a non-pressurized, non-cryogenic storage it has to be combined into another molecule and then catalyzed back out, real time, for use. And, of course, the ignition ratio range (4%-75% in air) means that it's very easy to accidentally ignite a H2 leak; substantially easier than most other fuels, though this is mitigated by it's density and ability to disperse in an unenclosed area.

Production is theoretically energy efficient as you can create it with hydrolysis, but the cheapest way of producing it, by far, is cracking of methane, which requires a high temperature process to create. It may not produce a high volume of CO2, but it perpetuates the cycle of exploration and extraction of gaseous hydrocarbons and the related environmental dangers and downsides.