Apparently the snowfall in Las Vegas breaks the all time record for amount of snow in December - at 3 inches! So it's understandable that they weren't prepared, but it was weather that wouldn't have closed most airports other than for the hour or so of complete whiteout.
It appears the main reason for closure was shortage of deicer, we met people who had been onboard planes, in a ground queue to go through the deicing process, but they ran out after a handful of planes!
We originally could only get rebooked for Friday, but after spending the night at the Flamingo, we called this morning and got booked on the last flight today - all flights to Seattle today seem to be running late, so it really will be late, they are currently saying 10:05pm. We are at the airport as there was only so much wandering around we could do.