Hmmm - Examples of when I use my spurs...
Mostly for lateral work and turns, and also to enable my aids for things like canter depart to become minute.
I can ask for either canter lead from a walk by just shifting my hip bone, dropping my outside leg, and moving my spur a whisker closer to his side. Up he bounces into canter.
I can move his shoulders, his rib cage, and his hind end with a tiny movement of my heel so my spur contacts.
When i'm doing a haunch turn (a 180 at a gallop) again all I have to do is drop my hip, bring my outside leg back, and open one rein slightly and close the other.
A rollback is similar.
When I have my spurs on, he becomes light as a feather - he is tuned in to the muscles in my legs tensing - I actually hardly have to touch him with my spur. It gives him 'incentive' to move off my leg.
Without the spurs, he will still do the manouvers, but he is sluggish and I need to contact him with my whole heel to get the response.
We also have some isues with losing momentum through turns - For this I use a soft cotton braid (A giddy up rope/wip wop) and once the turn is finished, I swing it around onto his butt. If I tried to urge him forward with the spur, he would jack up and get ****y, which does not look fluid.