Until fairly recently I strongly suspect that many childhood enemas were given, but not really needed. This probably continued until about the 1980s.
For starters, many were given enemas for ‘attitude adjustment’. With these, if a kid appeared ‘out of sorts’ … perhaps listless, had reduced appetite, was grumpy, not was not acting like a kid was expected to behave, many moms assumed the kid was constipated and the enema bag was the go-to ‘cure’.
Of course some moms preferred to give a spoonful of Castoria, a couple of squares of ExLax, or the dreaded dose of Castor Oil, but those all took many hours to bring relief. With her trusty bag, relief was just a few minutes away, and not only did it always work, but both the mom and the kid could SEE it work. With the laxatives a kid might not notice the connection between a spoonful of medicine at bedtime and a strong urge to poo in the morning, but not even the dullest kid can miss the connection between the enema bag, a butt full of soapy water, and having no choice but to poo at once.
Also, there was the placebo effect. If a kid was sick, then as now there were some ailments that really have no cure. The common cold is an example. But, doctors want to be seen to do something, even if the illness will get better without any treatment. An enema certainly meets this objective. Give a bag full of water and a pile of poo soon fills the toilet.