Recently there were a few blurps on Sheepdog-L about "working" dogs. I said my dogs were "working" when they did agility. They said since it was a sport the dogs weren't working. I guess they think they are playing.
I didn't look for these pictures; they were actually the first two photos I picked up out of a box of pics. Jet appears to be "working" in both of these photos to me. I think if he could talk he would tell you that agility is just as serious a job to him as his sheep are to him.
I think sheepdog trialing is just as much a "sport." Granted, we breed for good working traits.
We breed for sound structure, biddableness, the desire and stamina to put in a good days work. These good traits just happen to spill over very nicely into several different dog sports.
I think we try to think of livelihood (stock) and sport (agility, etc.) in human terms. I'm guessing our dogs don't know the difference. Who really knows? I don't, but he looks pretty darn focused in both photos.