Real talk: Opioid abuse. I somehow never became addicted, but I did use them recreationally. I did have legitimate medical issues (gull stones, before surgery). But sometimes I just liked the high. With that said, opioids can cause delayed poops. Many other factors too, like dehydration, not enough fiber and GI conditions.
But anyone that’s somehow purposely holding it that long should see a doctor, and counseling.