There is no demand
T Boone Pickens and others set up a consortium to facilitate natural gas as a long range truck fuel. The cost of the natural gas fuel vs Deisel was considerably less and now is probably a lot less.
The consortium included Flying J who has facilities all across the country at about 200 miles intervals. supply was readily and easily available. I believe the venture failed because the truck fuel consumers did not accept the bargain
CNG doesn’t have the energy content of diesel................
http://pointsandfigures.com/2011/04/27/natural-gas-vs-diesel/
Ford tried pushing CNG cars for city police departments. Atlanta got a few. Too many problems. Engines not as responsive. Logistical nightmare with delivering the gas. They very soon went the way of the dodo.