It was done in the 70s as a response to the oil crises. Turns out it only works for fleet vehicles working a set radius or route. And it’s still used that way (with some shortcomings) for fleets all over the US.
However - after a number of ‘genius’ individuals blew up entire city blocks trying to rig up home filling stations and a number of cars were involved in incidents that killed everyone in a 100’ radius because of tank ruptures and improper maintenance, it was filed away as a bad idea for the vehicle population as a whole.
Do you remember where you read these articles? My impression is that most natural gas related accidents come from crashing into natural gas pipelines. To my knowledge, Mexico's CNG conversions are completely unregulated, and I've never heard of spectacular accidents.