Wasting? Forget it.
People sleep different amounts. My workmate always believed that people need more sleep in winter, when days are shorter.
I wake when I wake, without alarm. For most of my life, I slept 4 hours a night. As I have got older, I now sleep about 6-7 hours some days.
Studies will tell you that too little sleep affects your memory, especially in children. I suspect that "too little" needs to be defined for each person differently.