Probably because PK offered direct routes between MAN and cities in Pakistan long before the mideast carriers came onto those routes.
PK started Islamabad in March 1989, Lahore in Autumn 1996 and Karachi late 1997. EK came along in November 1990. GF operated between November 1992 and March 1996. QR started March 2003 and EY in March 2006. Passenger numbers to Islamabad peaked in 2008.
AI started 2 weekly A310 via Rome in 1995 (wanted it to be 4 weekly 747), boosting to 4 weekly A310 via Rome in 1997 before announcing in spring 1999 that MAN was going to be getting a frequency increase as a "key destination" before pulling out end of summer 1999. Uzbekistan Airlines also tapped into the Indian market with a weekly service between 1994 and 1997 via Tashkent and I'm pretty sure that the up to 2 weekly SU services between 1987 and January 1997 was also targetting the through traffic.
Market size is something like combined 100,000 to Mumbai/Delhi.. now what routes have been recently launched at MAN with that market size?