One of my favorite fads of the past was the Pet Rock fad of 1975. The first Pet Rocks were born out of builder’s rock (gray granite) and marketed as if they were live pets. The fad lasted only about six months, ending in December 1975. The originator Gary Dahl had become a millionaire in +/-six months.
I like the tradition of wearing hats better.
There was a time when it was considered embarrassing to be seen in public without a hat on.
Both the habit of obsessive hat-wearing and of pet rocks were quite dumb. In fact, most 20th century fad were quite awful... Rock music is good though and that started out as a 20th century fad...
I could be wrong, but I would bet almost all fads look dumb ten years after they pass.