Final answer:
Parathion is preferred over paraoxon because it has stronger insecticidal properties, despite being more toxic to humans and having a shorter half-life in the environment.
Step-by-step explanation:
The reason why paraoxon is not used instead of parathion is because parathion has stronger insecticidal properties compared to paraoxon. While paraoxon is less toxic to humans and has a shorter half-life in the environment, it is more susceptible to degradation by enzymes. Parathion, on the other hand, is more effective at killing insects, making it a preferred choice for insecticide use.