For decades, the Pakistani authorities have been unable to establish effective tax collection practices. Currently, only one percent of Pakistanis pay their taxes and the country has one of the lowest tax-to-GDP ratios in the world.
Successive governments have avoided imposing stricter controls because they have been staffed by members of the same elites that are actively evading taxes. They are able to do so not only because of government inaction but also because of widespread corruption. In fact, it is cheaper for them to bribe than to pay their dues.