Why do so many contemplative philosophers "Sit-on-the-Fence" ?

Because they don��t trust their own philosophy. If they took a stand then what they believe in might be disapprove.

Are there "non-contemplative philosophers?"  (Aka Valley Girls That Don't Think but Act, as in the Mall dress store?  Their point:  we as Non-Contemplative Philosophers don't need to think, we need only to Act; double latte, please, and put it on daddy's tab.")

"Sitting on the Fence" is no vice if Sitting on the Fence means Holding a Balanced Perspective.  It may be argued that "Sitting on the Fence" is a marxian shtick wherewith the orally-fixated beer fan never elects A Profession or A White Collar Technician or a Blue Collar Trade, but sits in the British Museum looking for Evidence to support her Hypothesis that Work in the Future will be Orally Interchangeable, Baby going from Computer Programmer to Dentist to Brick Maker on three Successive Shifts.  Reality doesn't work that way, never has; even in the Garden--the true workers' paradise--the knowledge of how to dung trees was necessary (not too far out from the root structure, which varies from species to species, etc.).

"Critical method cushions" as issued by Educators may be "dudly do-wrong" if selfish.  One example:  the selfish misuse of critical as a superiorist notion (= agree with what I/we define as critical thinking or be wrong).  Such dudly do-wrong is simply another kind of uncritical thinking, hmpf.  True Critical Thinking might begin by divesting itself of selfish superiorism, and in genuine humility taking up the new name of Paul Thinking, aka letting this Mind abide which was also in Christ Jesus, for the purposes of Godly-guided Ideation as Plotinus and other such worthies have thought, being aware of the inherently limited or even flawed nature of human mentation when not bonded to One Mind Soul-realization.  Basically, "Critical Thinking" begins with taking up a name that is not so Logically Positivist...thereby declining to make the same arrogant or selfish claim that "My tool can beat Your tool," aka My God can beat up Your God," etc., etc.

Non-contemplative Party hacks apparently crucify those whom they ought be serving:  https://www.cnn.com/2019/05/08/asia/uyghur-xinjian...

An example of selfish "critical thinking."

Because it is the "job" of philosophy to raise questions, consider possibilities and foster discussion, not to provide absolute answers - which is obviously what you desire but aren't going to get, particularly with your pet "environmental philosophy". . 

The only dud around here is your brain, what little there is of it.