Because he is smart. If you have weekdays only reserve you're more likely to be pulled because there are only 1 or 2 people sitting reserve for a specific block of days. Weekends, including partial weekends, are staffed generously. I personally have the best experience with Thursday -Saturday AMs, but I can see Sunday-Tuesday PMs can be gold mines too. I'm honestly puzzeled reserve is still achievable at relatively low seniority. I've been bidding reserve exclusively since we got really over staffed, and my income and QOL ratio is better than ever.