There’s a very good reason why they call it ‘dope’.
Perhaps you should look up the origin of the term.
We could call alcohol dope for the same reason.
“One deficient in judgment and good sense.”
That sounds just like someone who has had a few too many.
Also of note:
“Dope was borrowed into English from the Dutch word doop, “sauce.” Throughout the 19th century it meant “gravy.” In the North Midland United States, particularly Ohio, dope is still heard as the term for an ice-cream topping, such as syrup. In the South, particularly in South Carolina, dope means “a cola-flavored soft drink.” Dope was especially used of those medicinal preparations that produced a stupefying effect, and it even became a slang term for the dark, molasses-like form of opium that was smoked in opium dens. Some of the common modern meanings of the word dope-”a narcotic substance” and “narcotics considered as a group,”-developed from this use of the word.”