Turkey's value to NATO traditionally was proximity to the Soviet Union. It was a great place to monitor signals, Very useful for keeping an eye on Soviet naval activities, and a great launching bad for short and medium range missiles.

In the wake of OPEC wealth and their funding of Islamic fundamentalists they were useful as a Muslim nation oriented toward the west that could act as an under the radar intermediary.

We no longer care about deterring the Russians even after the invasion of the Crimea and Turkey has stronger financial interest in being on good economic terms with Russia than any time in the recent past. Turkey has its own internal problems that no longer makes it terribly useful in the field of diplomacy.

Net loss in having someone will share information about Russia and its activities but they are pretty much lost already in diplomacy.