It's simply because the Turks are Turks, not Arabs.

Arab is an ethnic group, mostly defined by their use of the Arabic language. They likely came out of the Arabian Peninsula and spread across North Africa and the Middle East.

The Turks speak Turkish, which is completely unrelated to Arabic. They spread west from Central Asia and Siberia into what is now Turkey (as well as modern-day Azerbaijani, Turkmenistan, etc.)

Turkey isn't an Arab country in the same way Iran isn't an Arab country and Japan isn't a Chinese country: they are different ethnicities.

Because Turks are not Arabs. Origin of the Turkic people is Central and Northeast Asia. Some of them migrated to - what we today call - Turkey starting from the 11th century. Some of them still live in central Asia. Anatolian Turkish language, which commonly known as Turkish, borrowed a lot of words from Arabic, Persian and local languages in the Anatolia. Arabic and Turkish are very different languages in terms of grammer, syntax and phonology.