Originally Posted by intub8r

Maybe F or Y is the only fare bucket left on the flight?
Maybe you want the mile or point bonus that comes with a full fare ticket?
Maybe it's not a simple one way or round trip ticket but one that includes other layovers or stopovers and you want flexibility to change those?

I've never done it either but I can think of some examples as to why it might be done, besides for the ploy of accessing the gate / lounge and then cancelling.

Originally Posted by no2chem

As intub8r indicates, its often the only available fare last minute, especially on short haul flights.

What happens to me is that my destination goes WX (for example SFO fog during runway construction...) and I really need to get there, or I already purchased a last minute refundable fare anyway. If I see that some other carrier has not posted a delay on their flight, I'll go over and pick up a ticket. Sometimes my original flight ends up being faster, sometimes the new flight ends up faster.

So if my original flight ends up being fine, I just cancel the refundable ticket I just bought. After all, thats what they are for, right?