Agreed with SSC.
If it's an iso movement, doesn't necessitate a lot of weight or isn't the type of movement that requires too much coordination, I don't see why not if that's your cup of tea.
But if I ramp up (warm up) for flat bench, then move on to dumbbell inclines, I'm not hoisting the 120's my first set. I like to start with about 3/4 weight and jump up by feel keeping the reps around 3 - 5. Lighter weights and lower reps = little need for extended rest during this time, so it doesn't eat up a lot of time.
But, sometimes for iso movements I like to ramp up anyhow just to use the lighter weights/higher reps as a way of getting some blood and feeling into the target muscle for that exercise. I have trouble activating my biceps, so even if I do warm up with BB curls, I'd need to warm up/ramp on incline DBs so my body gets used to firing the target muscles for that exercise.
If you don't need to, then more power to ya. But it might cause trouble down the line if you try it out with the heavier money movements by jumping right into a top set without taking a few minutes to feel your way up.