I always get on a horse without spurs, if I don't know the horse that well, of course. But, come to find, some have just always been ridden with spurs, and respond only to that. They've become ingnorant to the leg, and spur is really all they know. (Lesson horses)
My own gelding, moves fine off of leg and seat, but sometimes for more advanced flatting, he needs a little extra. I own half inch knob spurs, and one inch knob spurs. I primarily just always use the half inch. That's all he really needs. I rarely have to actually touch the spur to him, but as long as he knows they're there, he moves off nicer.
He gets flat out spaztic with a crop.
So, spurs can be a touchy subject, and are very easy to mis-use but I don't look at a person with spurs on, and think their horse has issues.
"You're just as sane as I am."~Luna Lovegood.