There is another factor that springs to mind, that is the strong Temperance Movement which was evident in the Victorian period; this, coupled with the Victorian talent for hypocrisy does suggest that we may have hit on something here. A middle or upper class member of a temperance society would not want to get caught buying alcohol, think of the social stigma, so a respectable outlet as you say.
The inquest on my grandmother (1901) mentioned she used Mother Siegal's Syrup, a pharmacist friend found the ingredients for me, it had sulphuric acid as a base! Many of the stronger medicines in use in that period would now be clasified as Class A drugs, including many opiates used as pain killers in confinements, I believe today Queen Victoria would be described as addicted to opium.For another insight the Sherlock Holmes books give a view of drug taking in Victorian London.