the reason that i have heard and i can think of are these
with more than one set with the top weight you can progress not just in weight and reps but also in density, total volume and stuff like that
with lots of sets with the heavy weight it allows your CNS to get more adapt to handling the heavy weight
better for neurological adaption
helps develop form with heavy weight better than if you were just lifting it for one set a week
some people find it more fun as they can do lots of sets of deadlifts or whatever rather than just one then moving on to the next exercise
with more than one set with the top weight you can progress not just in weight and reps but also in density, total volume and stuff like that
with lots of sets with the heavy weight it allows your CNS to get more adapt to handling the heavy weight
better for neurological adaption
helps develop form with heavy weight better than if you were just lifting it for one set a week
some people find it more fun as they can do lots of sets of deadlifts or whatever rather than just one then moving on to the next exercise