The law usually reflects what people think is moral. Not all people of course, but a critical mass. Smoking weed is still widely considered immoral. Drinking was considered immoral by a lot of people when Prohibition started, and it still is by a smaller but still substantial number of people.

Jaywalking is more complicated, because there was a deliberate campaign to stigmatize it. I can’t recall if it was made a crime to promote the stigma or in response to it, but a sigma was definitely involved.