Again, societal differences between countries make direct comparisons difficult. I think you're mixing two arguments. My main comments about 19th-century drug use were directed towards the lower potency of the substances in those days. Doing drugs in a back alley has little to do with the legality or illegality of the substance being used. It has more to do with the individual doing the drugs.
British nobility are just rich enough to have decent places in which to indulge.
In fact, consider opium. During the early part of the century, opium was popular among both whites and Chinese immigrants. The difference was that whites liked to eat it, and Chinese people liked to smoke it. The first opium laws prohibited only the smoking of opium. This is little more than reinforcement of what I said in the previous paragraph.