If something works, you don't mess with it. Delhi Metro is one of the few things in the national capital that is world class, messing with it's revenue structures for petty political gains would reduce the quality of service. Everyone knows that nothing is truly free. The government can't simply print money at whim unless it wanna risk hyperinflation. Either it will come from the public and if it doesn't, then the quality of whatever service one is getting will suffer.