Why is it that people do get gallstones?

Not exactly known: Exactly why people get gallstones is not fully known. Ethnicity, older age, female gender, hormone therapy, high fat diet, obesity, rapid weight loss, diabetes, high triglycerides, and lipid-lowering medication can increase your risk. Cholesterol stones form when bile contains too much cholesterol, too much bilirubin, or not enough bile salts, or when the gallbladder does not empty efficiently.

Diet and heredity: It is multi factorial. Diet plays a large role, but so does factors you can't control. Being female, overweight, fertile, and rapid weight loss are well known factors. Additionally, blood disorders such as hemolytic anemias place patients at risk. That being said, the presence of gallstones alone is not an indication for surgery, it is only when those stones cause symptoms.