The reps don't matter as long as it isn't neural (max triples or heavier).
The reason for sets and reps is so that you have a guage, a constant that lets you know if you're actually really working more from week to week. The reason the routine works is because you're adding weight to the bar on a regular basis, and improving (using the same lifts for the same number of sets and reps, but with progressively more weight).