I heard Tommy Chong on a podcast share this story about meeting John in L.A. in the '70s.
We were at a party at Lou Adler’s house and I walked into the bedroom to find a place to get high and John was sitting on the floor, like huddled on the floor like an early caveman… and I lit up the stinkiest joint I’ve ever had in my life, you know real poor quality that just smelled like manure. So I handed it to John and he turned it down. He said no, he was on probation, he was getting deported or something.
Makes me wonder if he turned down the joint 'cuz it stunk (Cheech and Chong tell a story about getting high with George and his high quality "Beatle weed") or because he actually wan't smoking in those days. And if it's really because he wasn't smoking, then all I've got to say is that's too bad. He would have avoided so much trouble if he just lit up instead of drinking so much. Also, the John/Paul impromptu studio session wouldn't have been such a "Toot and a Snore" – it may actually have been more inspired. We know he did coke, so I don't know why he would have avoided weed...
It probably had to do with the reason why he was all huddled up on the floor. In another version, May was there and so was Rod Stewart.