Are you sure this is Marriott policy or just the hotel(s) you have looked at? I just tried a dummy booking for a Courtyard in Omaha for mid-June and the cancellation policy was 2 days before arrival.

The only rates that were different were the Advanced Purchase rate. Make sure you are looking at the tab "Standard Rates" and "Prepay and Save" I have noticed that my browser defaulted to the Prepay tab so maybe that is what you are seeing?