I think that is exactly the reason why they aren't brought back !
As is the reason that now - we've forgotten about these things too & even the MQM raises this issue only for political mileage if they ever do raise it !
What is an even great reason is that most Pakistanis don't even know about this; I can't recall meeting anyone knowing about this except a handful of people who had studied about Bangladesh, the '71 War & stuff, knowing about this & even then at times they didn't know about the extent of the issue here !
Most thought that the Biharis are well integrated in Bangladesh without any issues & one even chuckled in disbelief when I told him about the Refugee Camps they have all over Bangladesh or the number of Stranded Pakistanis there are there !
Ideally the stranded Biharis should be relocated to their homeland, Bihar & UP! But they most probably hate India, so not a good idea.