This is nothing new. NW has been doing this for years!

On Sundays of 3-day major holiday weekends, like Memorial Day and Labor Day, for example. Also on Thanksgiving Day and the Friday afterwards. It is all very predictable, really. If there will be no "business" passengers traveling on a given day, then revenue is going to be very low and it only makes good sense to cut back on the number of flights offered.

The good news is that the schedule changes have been announced well in advance so that everyone can alter their plans by a couple of hours and still get where they want to be on a given day. It might be a minor hassle for you, but NW (or any other airline) does not revolve around you and your needs. Only THEIRS!!!!