Back in the early 90's when I flew YYZ-AMS-SVO frequently, I could get an upgrade on KL about one time in three simply by dressing well, being pleasant, and asking nicely. It helped flying on busy days when coach was heavily overbooked and they were bumping people anyway.

Times (read: airline economics) have changed, and airlines have realized they can sell the upgrades or capture frequent flyers with those seats, so it's difficult or possible to do these days unless one is lucky and on a flight heavily overbooked in coach.

There's nothing unreasonable about asking if something can be done, particularly when the airlines have been willing in the past to do it.