The real reason I suspect is purely monetary.
No fuel dump means less pumps, piping, valves and weight.
More room for paying weight, which over the course of the airframes lifespan could almost pay for a tire or two.
The FAA dropped the fuel dump requirements if certain performance standards could be met, which with modern engines, was not hard to achieve. So, if it is not required by regulations, why waste the money. Planes are built tough enough to take an overweight landing, depending on how overweight dictates the follow up inspections.
With the P3, we could make a total of 10 landings between certain weights (103,880 - 114,000) before having to do an overweight landing inspection, or one very heavy landing (>114,000) which would invoke the inspection.
I have spent many hours in the pattern @ 1200 feet above Moffett Field burning fuel down so we could make a landing. This would usually be on a 12 hr mission when we had full crew, fuel and sonobouy loadout and we had a malfunction soon after takeoff that required a RTB.
bob