For me it's systemwide upgrades. My job all but prints miles, and while the credits would be nice, if I'm booking cash fares (especially on long haul flights), I want to have SWUs ready to use.

I don't view them as strictly for long haul international either. If I can get a two-segment domestic itinerary (where both segments are over 2.5 hours) to clear in advance, I'm likely using the SWU. Especially if it's a work trip.