Karachi isn't entire Pakistan. You have to shove your Karachi centric biases everywhere.
Your bengali maasi's kids studied and got opportunies ( salesman, electrician etc ) cause THEY LIVED IN KARACHI WHICH IS THE ECONOMIC HUB OF PAKISTAN. It doesn't matter how poor they were, they had access to education and jobs around them. They had opportunities to improve their life, being in a major city. You think Baloch and Pashtuns in Awaran, Turbat, Khuzdar, Mastung, Qilla Abdullah, Chaman, Loralai have that?
That isn't the case in Balochistan. You either have to leave the province if you are lucky enough ( like me ) or you stay there and get into all kinds of nefarious activities as there is no economic activity happening there or jobs or hospitals or nothing.
South Punjab is improvished, no economic activities or job unlike Karachi and reason it's Daaku territory and banditry happens there. When people have nowhere to go to, or improve their life ( as your maasis children did ), they get into the life of crime.
Karachi is 1000x better. Har cheez may Karachi kay bias ghussana chor do. You never have been to Balochistan to interior KPK.
Foreign elements use this poverty, lack of infrastructure as propaganda element to rile up the youth, give them money which they desperately need and you get an insurgency. If you wanna eradicate insurgency, you go to its roots, not to shove your bhaiyya ethno centrism everywhere.