It is not that simple. It is all about cost reduction. If we are producing a fuel that is profitably available say for 60 rupees (a unit) why link it to an imported fuel (gasoline) which is for 100+ rs (a unit). Transport is also an important sector of overall economy. If people and things are not able to move economically than it raises the cost of production and living too.
This is more to do with corruption than economy. The corrupt administration is looking for more bucks in kick backs and commissions through increased petrol imports mindless of the risk of depleting already dwindling forex reserves. Shortage of gas is thus artificially created and CNG prices jacked up (without giving any benefit to exchequer) to force people to buy expensive gasoline.
If gas is so scarce then why it is only in Punjab? Sindh shuts CNG stations only for 24 hours in a week, in KPK no CNG off days and it is available 24x7x365 and same is the case with Baluchistan. Punjab is being punished because there is opposition government.