Warm-ups are not extra working sets. A lifter preparing for a heavy squat may use several progressively heavier ramps; a light isolation exercise may need very little specific warm-up.

The goal is to arrive at the first working set physically and technically ready, not already tired. If you lift heavier weights, multiple warm-up sets is often necessary: a light set for movement rehearsal, a heavier set for load acclimation, and then an even heavier set for potentiation. Doing multiple warm up sets helps to avoid injuries.