There is a general finding that women go into engineering fields (and other relatively high-paying fields) more the poorer their country is. Neither "software engineering" nor "India / Pakistan" is an exceptional case; there is no reason to look at the specifics of the field or the region.
Usually the theory is that women everywhere hate engineering, but poor women may suck it up and go into engineering anyway because they need the money.
I agree this has an effect as well - software engineering is one of the few fields which provide good living in those countries.
However, coming from (relatively poor, but relatively gender-egalitarian) Eastern Europe, female engineers aren't anywhere close to the amount in e.g. India and Pakistan, so I don't think it can explain the disparity completely.
Usually the theory is that women everywhere hate engineering, but poor women may suck it up and go into engineering anyway because they need the money.
In fact, that was pointed out in this very thread a couple hours before your comment: https://news.ycombinator.com/item?id=41716578