Well, first of all, Tolkien was a pipe smoker. He smoked tobacco on occasion. Given his time frame and the nature of the fellow, it’s a pretty safe bet he wasn’t a dope smoker, for all that college freshmen would remark why Bilbo’s last name was Baggins… as in “nickel bag… get it?”
As one who came to the movies via the books, it never occurred to me that the hobbits were getting conked. Hobbits are fond of life’s little pleasures, remember? Dancing, drinking, six meals a day when they can get them… and a good smoke. I quit smoking years ago, but I still like a good cigar on Christmas. I have no doubt also that they really like to screw like mad minks, too, although Tolkien was too genteel to remark on this. “Simple pleasures,” indeed.
To the best of my knowledge, marijuana was not among the simple pleasures commonly available to early twentieth century Englishmen. Maybe the good Prof. T knew about it. Maybe he didn’t. At any rate, I’m pretty sure he never meant it to be part of the book.
Pippin is an idiot because Pippin is an idiot, not because he smoked a ton of weed. “You smoke too much,” used to be a common admonition, back before cigarettes became the most common form of tobacco use. Used to be, tobacco use was considered something like alcohol use – something you did occasionally, or in the evening, NOT straight through the day! Hence “smoking jackets” and “smoking rooms”. This is something Tolkien was familiar with.
I can’t speak for Peter Jackson, though, who, judging from his looks, may well smoke a pound a day (although I doubt it; potheads generally aren’t as productive as Jackson has been). Jackson may well have intended the “weed” references to appeal to potheads… or not.