The shuttle flights get a ton of stand bys and walk ups and the list really can change moment by moment. I have done this many, many times and its always a crap shoot. In this case you were trying to make an earlier flight, arrived almost at door close time, and it looks like they were already processing stand-bys. Just because they didn't drop everything to process you does not make it a "horrendous experience". You didn't get on an earlier flight so I assume you made it home on the flight you had booked, what's the big deal?