If you don't let people build new pipelines....
The more conspiracy minded note that Berkshire Hathaway is benefiting mightily from this: https://www.google.com/search?q=berkshire+hathaway+railroad+...
The more conspiracy minded note that Berkshire Hathaway is benefiting mightily from this: https://www.google.com/search?q=berkshire+hathaway+railroad+...
The real problem is the price (i.e. excess supply and lack of storage capacity):
http://www.eia.gov/dnav/ng/hist/rngwhhdd.htm
Natural gas has been down for a lot longer than the oil price, and even with hydraulic fracturing there hasn't been much incentive to produce or capture the gas. The deeper shales in Ohio and Pennsylvania produce other hydrocarbons along with gas, so they were seen as a better bet (up until a year or so ago anyway).
The railroads (and utilities, and really everybody) benefited more from the drilling enthusiasm of a few years ago than they ever would by holding up a pipeline.
You don't seriously think companies are going to waste millions planning out a new line if they have no idea when (if ever) it would be approved.
When gas is over $7 and oil is over $80 then there might be some interest, but it is going to be a while.
Natural gas pipelines most certainly run though major cities.