Because they are illegal.
5 Billion Rs licence is awarded to each DTH provider which proves investors have enough money for the DTH. Moreover, all the DTH are private DTH and Government of Pakistan is not launching any DTH by their own which means even if Pakistani Government has no money it doesn't matter because they will ultimately collect the money from the DTH providers.
Foreign DTH and brands are not allowed in any country. For example, in India it is illegal to use Sri Lankan DTH Dialog TV and same goes for Sri Lanka as you cannot use an Indian DTH while living in Sri Lanka.