Again, without some systematic analysis, I'm not sure I can answer that for you. I would have to start by first asking this question, which I will undertake to do: do we know how many foreign nationals we have in our penitentiaries? Again, you have to bear in mind that some individuals may be in prisons without disclosing that they have citizenship in another country or indeed that they have dual citizenship with Canada and another country. So when we look at the figure that 127 foreign nationals have been transferred back, I think we do need to find out what the context is: 127 out of how many are here.
As to why many of them do not ask for transfers back, again I couldn't draw any firm conclusions without doing a bit more research on that. They may have in general quite short sentences and they're prepared to simply do their time and then leave at the end of it. I'll certainly look into it and get back with as much information as I can.