Kissing Quran

[Karbala]

The hadith in the article is an interesting one and something id like to discuss:


here it is:


Yahya related to me from Malik from Hisham ibn Urwa from his father that Umar ibn al-Khattab said to the corner of the Black Stone while he was doing tawaf of the House, "You are only a stone, and if I had not seen the Messenger of Allah, may Allah bless him and grant him peace, kiss you, I would not do so." Then he kissed it.


So Umar kissed the black stone despite thinking it is ONLY a stone. Why did the Prophet(saw) bother kissing the stone if it was ONLY a stone? Is the Sunnah simply there simply for the sake of us to copy it like robots?