The problem with holding in stool is that the more you deny yourself going to the bathroom, the more fluid is absorbed from the stool in the bowel. It then becomes harder and harder and harder. And then, because it is painful to pass, people don't want to go to the toilet and a vicious cycle occurs.
There is a clear gender double standard around hygiene that ties into parcopresis. Women are socialised to be more disgusted by excretion and excrement, and to be more concerned about the cleanliness and purity of their bodies and eliminating its smells.