So, When Should You Actually Start Getting Colonoscopies?

Colonoscopies help doctors find ulcers, polyps, tumors, and inflammation in the colon and rectum. But the Centers for Disease Control and Prevention recommends that starting at age 50, people get colonoscopies every 10 years to check for abnormalities and colon cancer. Why would someone much younger than that get one?
Actress Bella Thorne, 18, just had a colonoscopy done, but the procedure is more common among people much older than her. Is this something the rest of us should look into, too?