Synthetic drugs came about because they fell outside legislation designed to control the different classes of drugs.
The police could not prosecute because there was no law to cover synthetic drugs in the early days.
I saw the slow increase in the damage caused by synthetic drugs as I worked in Substance misuse as a methadome dispenser. Rather than woking predominantly with heroin addiction, clients were presenting more and more with synthetic substance addictions.
For me I would like to see all drugs legalised so that the consumer has a safe way to use drugs of their choice.
I used to smoke hash in the 80's from as far away places as Pakistan, Afganistan, lebanon and morocco.
Now it is all genetically modified skunk which is 10 times stronger than the proper hash I used to smoke.