Handlebar mounted water bottle cages disappeared when everyone discovered that with proper pegs you could put a frame mounted pump right under the top tube. Up to that time (sometime in the 70's) everyone put their pump next to the seat tube. The pump blocked the space necessary for a water bottle cage.
Also, racers in the 60's believed that drinking too much water while riding made your legs heavy. Believe it or not, we'd do long training rides and races with one small water bottle. Not be out done, marathoners didn't drink or eat during a marathon in those days. Gatorade made its first appearance in 1968 but we all avoided it because it tasted terrible. If I was getting a bottle handed up, I wanted Coke or Pepsi.
Del Mar CA