Sliders not only enhance the length and 'prettyness' of a stop, they keep the horse from getting sore hocks, stifles and other hind leg lamnesses. Many calf ropers and heelers are now using a smaller slider than a reining trainers, but they have found that the extra 'give' and 'float' that a 7/8" or even 1" slider affords the horse is enough to help keep them sound.
The 'hard' stop where a horse is bracing with straight, stiff hocks to help him get stopped is so much harder on a horse than the stop where a horse's hocks are flexed and close to the ground and the front end is free and elevated enough for the horse to take a step or two even he is a calf roping horse.