Part1- comparative analysis
I understand you are not generalizing, and I want to make it clear it is not an attack on what you are saying, but I will use this to demonstrate something.
see, so there is skepticism, because you see some guys go crazy once they get here, and thus girls are put off by it etc etc.
by the same token, local guys get turned off by what they see as some local pakistani origin girls go crazy, and then these guys or their mums paint the local girl population with the same broad brush.
point being, these reasons are only as valid as we let them be, everyone has to be viewed as an individual.
As far as guys staying here, their reasons to marry someone local can be from a number, they will stay here, regardless of who they marry, many of these guys have obtained H1 and are getting greencards on their own, but if they are building a life here, it may make sense to find someone who is comfortable with the lifestyle here. the ratio of Pakistani guys to girls who came here for education is heavily skewed towards guys. I dont know how the situation is now, but at one point if you had an H1 and married someone from pakmanland, the paperwork and wait time to get her to come over was pretty bad.
part 2- personal anecdote
I have some personal experience with it, my wife’s cousins and the ring leader one chica engaged to her cousin tried to dissuade her from marrying me by telling her I was a player, party animal and what nots. The funny thing about that was that not only were they right, but they did not know the half of it and had some inkling of my grad school days, and not my undergrad fraternity days which my wife had heard all about from me anyways. however unlike guys getting here and getting freedom and then going bad, I arrived bad, and actually probably tamed down once i got here.
It boils down to views about life, I would never pretend to be some conservative type of guy and it was always laid out for all to see and know who I was and what I was.
I suppose some baycharay acchay bacchay desi bhai log got ignored like a big dog due to stereotypes set by people like yours truly 
if anyone of them is reading this sitting in gujranwala mad because his chica’s parents in US said no…dude.. I am sorry.
part 3- vouching for shareef desi guys.
My experiences have been that the vast majority of guys who come from Pak are basically shareef ppl, I know this because I was unable to corrupt most of them with my influence. and this too from unis that were in 30K plus student populations so large numbers of foreign students there as well as local desis.
Part4- misc after thoughts
PS: it did not help that her cousin’s fiancee who was all campaigning against me was then caught making out with some dude in the backseat of some car
PS2: Indian chicas?? man why why why do these guys from pak go for indian chicas, when as an international student you have costa ricans, argentinians, greek, dutch and what nots..desio guys really need to broaden their horizins