Why doesn't everyone have one of these?

The best way to disassociate water for fuel is wind, wave, or solar power. This because the energy needed to separate the H from the O is greater than the energy you get from burning it. So you'd need a power source that will pay for itself over time and then provide free power.

It's be easier and I think better to use the newer generation of batteries and an electric motor. They can last for more than a few years costing you only a few grand every three to five years to replace.

Hydrogen as a fuel for an Internal Combustion Engine (ICE) is all well and good but it does nothing to over come the inefficiencies inf the whole system. The ICE is a terribly inefficient power-plant. Between the reversal on inertia of the pistons and wrist pins and collars etc and all the friction almost three quarters of the energy an ICE produces is consumed just keeping the motor going. An electric motor is has only bearings for moving parts and the inertia of the commutator and windings to maintain. There are no inertia reversals and the friction is insignificant. A 20 HP DC motor can keep an average vehicle at highway speed just fine.

I rather suspect that the potential if Hydrogen is not here today but will maybe be realized in the future when some one figures a really slick way to disassociate the constituents of water cheaply.

There are so many innovative inventions that get swept under the rug, so others can fill their pockets. It sucks....well not for them