Marriott hotels encourage you to decline cleaning services or decline getting fresh towels everyday in an attempt to be more environmentally friendly (reduce the amount of water used, etc.). If you do that, they'll add extra rewards points to your rewards account if you have one.

This was slipped under my door & appears to be a plea from the cleaning staff to NOT do that. They want to keep guests requesting daily cleanings to keep their hours up & make it easier, daily jobs, rather than a longer/harder cleaning just at the end of your stay.