Dinner is the largest meal on most working days because it is the only slot with any room in it. In the morning you have somewhere to be, the kitchen is cold, and you are the only one awake. At nine at night, you are already sitting down, other people are in the room, and there is no next appointment.
Then it loops. A large meal at nine means very little appetite at six-thirty, so breakfast is coffee, so lunch is thin and rushed, so by four in the afternoon the sweet thing looks reasonable, and by nine you are eating the first proper meal of the day again. It is just a loop, and loops open at their weakest joint.
The weakest joint is the morning, because it is the only part of the day that nobody else has already booked. Your evening belongs to your family, your afternoon belongs to your job. Twelve minutes before seven in the morning belongs to you, and it is the cheapest twelve minutes you own.