And why can't you earn points for the room charges? Because the program rules specifically prohibit such points earning:

From Section 7 of the Point Earning section of the Terms and Conditions:

"Point accrual is limited to individual travel and the room must be paid for individually by the member. If the member attends a convention or group meeting and individually pays Marriott directly for the room, he/she will be eligible to receive points for the stay. However, contract rooms, rooms reserved by corporations on an ongoing basis, master-billed rooms and rooms booked at the Marriott associate rate or friends and family rate are not eligible to earn points" [Bold emphasis added.]

Note the wording doesn't just preclude the person staying in the room from getting points. No one gets points for the individual room charges. You get the meeting planner points instead.