What are some good reasons that have worked before?
One reason is if you have found a job in Canada that requires citizenship. There are some jobs (typically in government) that require citizenship for a specific kind of security clearance or for other reasons.
But you of course need to meet the residency requirements at the time you apply. Urgent processing doesn't work without it. So this doesn't give you a path for applying early. Just a potential path for faster processing once you qualify.
There's a thread in this section of the forum where people are discussing their experiences with urgent processing. I would recommend you find that thread and read through the reasons. That's the best way of sorting out what has and hasn't worked. FYI - wanting to work or study outside of Canada is not an accepted reason.