Ever see a working cowboy carrying a whip? (That is, a riding crop for use on the horse being ridden.) Or indeed, just about any riding activity where you'd need to use your hands for something else? So I think I'd argue that they're not really necessary.
Ever see a cowboy riding with spurs? I have. And while he may sometimes use the spur for a discrete cue, he will also use the spur if the horse refuses to move off of his leg cue. If you want a horse to be dull to the leg, let him discover that he can ignore your squeeze. And if there is no possibility of anything beyond the squeeze, except perhaps endless kicking, then the horse can learn to ignore you completely.
When I took lessons a few years back, there was a horse I could kick with my heels until my legs ached, and he wouldn't go above a walk. But if I got on him with a crop in one hand, he would do anything off of light leg pressure. Hmmmm.... And that was why the instructor had me ride him for 30 minutes kicking without result. She wanted me to see how quickly he changed when she handed me a crop, and to understand that a crop or whip, used right, makes your horse MORE responsive to your leg, not less.
Since Mia is a pretty willing horse, I don't carry a whip in my hand. I don't wear spurs. But I do have an option available if she decides to be lazy. She doesn't decide to be lazy very often, and I do NOT want her to learn. And believe me - just as she learned to ignore a snaffle, she is capable of learning to ignore my leg. That is the joy and terror of a reasonably smart horse...