Aside from the petro industry doing everything they can to hold it back, there was one genuine technical hurdle with hydrogen fuel that I'm aware of.

The problem is called "hydrogen embrittlement". Because hydrogen is the smallest atom, some of it can literally seep into the metal canisters that hold it. Over time, the hydrogen soaked metal becomes brittle; A serious problem when that container is holding pressurized, highly explosive fluid.

I remember hearing that there were several technologies that were being worked on to combat this problem but I don't know where they're at with it these days. Bottom line, it's not a viable fuel if you have to replace your gas tank on a yearly basis to avoid having your car blow up.

Regardless, I have little doubt that they could resolve this issue if they really wanted to. The petro industry bastards won't move to any new fuel technology unless they're ready to make the maximum amount of profit from it.