I've lately been reminded of the importance of not trying to kill everything, including not trying to get rid of all the aphids. A few aphids do not slow plants down very much. They are only damaging to plants when it becomes a major infestation, so the plant is pretty covered in them. That's the time when you need to do something to slow the population growth down to give the Garden Patrol a chance to catch up. But if there aren't aphids (and other stuff) for them to feed on, the ladybugs and other members of the Garden Patrol will pack up and leave for greener pastures. Then when the aphids come back (they always do), there will be no controls for them around. AND the honeydew that is excreted by aphids, scale insects, mealybugs turns out to be an important part of the food chain. Not only do ants like it and farm the aphids for it, it feeds many different bees, wasps, flies, etc. including the parasitic wasps and flies that help control other bad guys in your garden.
Every part of the system is necessary and important!