lol well at least SJ is usually run on fairly forgiving surfaces (grass or a properly surfaced dirt arena) so you don't HAVE to shoe. I have seen horses jumping 4'+ in competition, barefoot, and turning the tightest lines on the best balance. And winning. Conversely I have also seen horses jumping 2' that couldn't keep their feet barefoot and HAD TO have shoes with studs... AND it depends on the surface, too, because some surfaces are more slippery than others.
I rode at a SJ day once where there was a hint of dew on the grass/weeds, and later some very light misting rain, and the pony I was on slipped twice going in a straight line... he was barefoot and his feet were really slippery (slipped ALL the time road riding when the other horses were absolutely fine) but we weren't the only ones. That day, on that surface, I would have preferred to have shoes with studs. That pony went totally barefoot and never had a problem at any other shows we took him to, even though it poured buckets at several.