Why would we give any land fought in defensive wars?
Because this land still officially belongs to Syria according to international law. The moral and legal justification for Israel occupying it is the strategic value of the place in fending off threats from Syria. That logic no longer holds, but you keep the Golan anyway, in spite of a lack of a "direct threat".
And just for the record: I'm mostly pro-Israel and totally agree with you guys asserting yourself in a hostile environment, agree with you guys doing what's strategically smart. My argument is just that in doing so, Israel has to occassionally be a dick to its neighbors and engage in behavior which takes place in a legal and moral grey zone. Which brings me back to my earlier point that Israel only "is no threat to its neighbors" as long as there are no conflicts of interest.