3) Why is it difficult to stop drug trafficking?

Because drugs are addictive.

Explanation:

Mostly the one who use drugs are teenagers, with increased level of hormonal activity. Even if an individual take the drug once, his brain would force him to take more. this is how drug demand gets increased day by day.

A teenager who learns most of the things at this age gets easily addicted to this bad. and hence it is very to stop it in either way