Because don‘t sleep much. Never did.
When I was an infant, my parents reported to my pediatrician that they were happy to report I was getting 8 hours of sleep. The shocked pediatrician replied that infants are supposed to sleep whenever they weren’t eating or playing- @20 hours per day.
When i had a temp job at Texas Instruments, I turned off my TV at 3AM, got up at 6:30AM, and got to work at 8:30AM. Did that for a month...and set a productivity record at my task.
Every once in a while, I sleep in, and as I get older, I find myself sleeping a bit more than before, but I’m still averaging 4.5-6 hours a night.
As I write this, my alarm is set for 9:45- to take a particular medication- and my second one is set for 10:30.