It isn't the main reason, but I do feel safer in a saddle. It's because you can't fall out of it and into your harness. I think most humans, even if you're wearing a harness and aren't especially afraid of heights, aren't like "yeah, that would be fine/fun, I 'm not worried at all now in my lizard brain regarding being 20 feet off the ground balancing on a little square of metal while the wind blows me around."
However, your lizard brain does recognize the comforting goodness of your butt cheeks being gently supported by fine American made textiles.
I didn't know why before, but after a long sit in a normal stand, I had a mental load/stress that was like "I need to get down from here." I think now that despite not being afraid of heights, I had to be vigilant the whole time not to fall off my stand. After 12 hours, it took a toll. I think everyone is afraid of heights to some degree, just like we should all be afraid of tigers in the same room with us (reasonable and not a phobia at that level).