Erik, buddy... you gotta cut us some slack! Those trees where you live... they don't make spurs long enough to get through the bark on those, do they? Yeah, I've only ever seen one tree die (a few years after) from being spurred to death. It was a little 8" birch or aspen with bark as thin as the homeowner's skin. He bought an old lineman's belt and a buckstrap, and would spur up and down that thing to prune it... cut a branch, come back down and look at the tree, go back up and cut another branch... gawd, it was so funny my sides hurt for a week from laughing at this clown. It eventually had so many strips of bark missing and carpenter ants, borers, bark beetles and who knows what else living in it that it died.
But... I figure spurs on a tree when you don't need to do it is still probably not doing it any good, and I think that's the main reason it's frowned upon. If I think it's safer, I'll spur the bastard. But the no-spurs approach does sharpen the climbing skills, too. And, I hate climbing in spurs on the elms and cottonwoods around here. You can practically walk around in the tree, with some of them, they're so spread out.
You live in the land of the real giants. I've never climbed a tree over 90' in my life. There probably aren't more than a dozen trees in this state that are taller than that!