Answer by
LeheckaG (1826)
Bellagio uses MGM/Mirage-player's-club-card to track comps-earned which are based on number of hours you bet and how much on average you bet (at risk) per hour.
Cheaper-comps like drinks & food are easier to earn than more-expensive-comps like rooms.
Because card-table-bets are usually-higher,
you earn more-comps at cards than slots.
Betting $90 to $250 per-hand for (4)hours can-earn a room-comp.