There is also the customer services aspect to consider. Alienating regular passengers who have pre booked / assigned with online checkin seats. There is a perceptible difference between justified operational needs (mother needing bassinet seat or even maybe CIP/VIP or inop seat and just to save a few kgs of fuel. IMHO. It might be short sighted to pee off the passenger if they've gone from a nice aisle seat to a sh1tty middle seat at the back with no recline.
I know that, since it happened to me in a previous "life" and KLM/NW got pushed down the preferred routing list from several flights a week with that particular carrier.