Look at all of the artwork that was used on the boxes that fountain syringes came in; attractive lady, outline of a female, flowers, etc. It's not hard to figure that the manufacturers knew that their biggest users were women. That, coupled with the diaphragm and vaginal jelly, made douching very common.
When I sold for the S.E. Massengill Co., we'd attend district sales meetings where we would be inundated with video slides of marketing statistics.
The optimum age for buying our product was the 18 to 35 year old female. The "pill" had just been on the market for a brief time, so lots of women were still using diaphragms.
One of my most pleasant tasks was to put a free packet of powder into every syringe in a pharmacy; even the bulb douche syringes. That was a fun product to sell.
When I was a preschooler, my mother would call her sister everyday and one of the statements that would always be made was ,"Did you douche".
That was their code word for did you have sex last night. Since our bag was hanging over the towel rack so often, I knew my mother was using it for something, but I knew she hated enemas herself. If the order for one came from a doctor, it must be gospel. Eventually, sometime in grade school I figured out that the big black nozzle was used to wash out something other than my guts. Maybe that's where I made a connection between sex and enemas. By the time I was 9, the "E" bug had bitten me hard.