Snooze Quandry

I'm one of those moms who has always gotten her kids up for school. Well, let's face it, they've only been in school for three years, so it isn't that long of a tradition. Now that Grace is 18, ready to go off to college, and Earl and I are preparing to leave for vacation, I've been letting them set their alarms and get up.
Grace is very reliable at this. She sets her alarm, gets up and jumps in the shower first.
Tucker also is fairly prompt at rousing himself.
I came back from the Y this morning at 7 and he was in the shower.
Spencer is another story. This boy sleeps hard. He always has. When I was waking him up, it became a yelling thing nearly every day. I'd start gentle. I'd call his name, shake his shoulder, turn the light on, throw a cat onto his bed. He might open his eyes, he might respond, but he wouldn't actually get up. Then 10 minutes before we were leaving, I'd be shouting and he'd be shouting back.
"You're going to have to walk to school. You're going to be late," I'd warn. Somehow, he always manages to stick his head under the shower, brush his teeth and run out the door to the car.
Most of the time he doesn't have time for breakfast. If I were 6-foot, 3-inches and 150 pounds, I'd want breakfast. Sometimes he'll grab a granola bar.
Now that he's in charge of waking himself up, he sets his phone as an alarm.
"I hit snooze four times," he explains. That's his plan. To wake up and turn off the alarm four times.
I just don't get it. Wouldn't it be better to sleep straight through until the absolute last minute you have to get up? Why wake up 15 minutes early, hit snooze, then five minutes later, hit snooze.
See, I just don't understand the appeal of the snooze button. It doesn't seem logical.
Can anyone explain it?