Mostly you see with most routines, the big 3 are done with low reps then most of the assistance is done in higher reps. is this because if you were to train all your assistance exersises with doubles and triples it would burn out your CNS??
Basically yes. You also want to save the wear and tear on your body for the big 3 lifts. Sometimes you can cycle in assistance exercises as your ME movement depending on your weak points.