It's not like petroleum is all that nice though, it's just that the handling around it has been pretty much perfected over the decades. You can collect spent sludge at the same place a scooter has to come anyway to refill and then re-hydrogenate the sludge into fresh paste.
The big difference, of course, is that petroleum doesn't explode or combust when rained on. Aside from sparks or ignition sources, it can sit in a bucket or puddle and be happy staying put.
Neither does this substance though. It releases hydrogen when in contact with water, not explode or combust. It might, of course, explode if sparks are introduced but the same thing can happen to hydrocarbon based fuels.
In any case, what a substance does when rained on is not very relevant for a fuel that is kept in a fuel tank at all times. By the time it's exposed to the weather, the vehicle must have crashed and in such a circumstance most safety guarantees are out of the window anyway.
