Why not do both? That is help out the social sector as well as the Pakistani military. Why don't you guys use your multi-billion dollar defence budget for social uplift only as that would be much more meaningful than spending on gleaming new MKIs and MMRCA? (God knows people in India need this money). The reason is an obvious one. You have received massive aid in the past from the Russians and even Americans when faced with an external threat (that of China) and you can't understand why Pakistan needs to do the same?
By "you guys" I assume you're talking about Indians. I can't speak for them directly, but from what I understand India does not have foreign aid when it comes to military procurement programs for the MKIs and MRCAs, which means they have to get these on their own (as they should). Also, Russian aid of yesteryear came primarily in tech transfers, subsidized production licenses and such; not monetary. India's military expenditure is lesser than the 3% GDP norm while the expenditure on the social sector is rising exponentially as we speak, so they're certainly on the right path. Also, their armed forces are undergoing a comprehensive upgradation program which although conceived in 1999 (post Kargil) couldn't be achieved until now in the light of over a decade and a half of economic growth... as it should be.
This nonetheless has nothing to do with the Pakistan model, which is totally dissimilar. Nor are the problems faced by each country alike (I'm not sure why India was even brought up in this situation). The acuity of the societal problems marring west Pakistan are far greater than most other places in the world right now and every available dollar should be spent on the social sector. Unless the populace inhabiting these areas are offered credible alternatives to radical religious organizations in the form of schools, employment, law & order, health care, infrastructure, etc. the bleak picture will never change. To make this happen billions of dollars are needed (NOW), and it just so happens that in the case of Pakistan there is a way to acquire these funds. It would be foolish not to do so.
Lastly, the military need not be left in the dust. More affordable Chinese alternatives are being procured for the armed forces; so there really isn't a need for the F-16s.
It would also be unfair to solely lay the blame on Pakistan. There is undoubtedly a push from US military corporations to further their sales of expensive products, and foreign aid packages to troubled third world nations have historically provided the best opportunities to achieve this (dubious) objective. Given the influence these companies have with public representatives (particularly in this administration) this is turning out to be a cash cow for them. All of this has to stop ASAP.