One thing I did read about this was that it worked best with fuels of natural gas and the like. Perhaps the lack of infrastructure for this fuel prevented any sort of penetration of the technology in modern designs.
It might also be too soon. If the technology needs to be proven, the design cycle for modern cars is about 5 years or so isn't it? If it took 4 or 5 years to prove out the technology, work on it's issues, like sealing, measure it's longevity, performance, fuel economy, emissions performance, etc, etc, it might not be ready for inclusion yet.