Because common sense requires thinking before reacting, listening before replying, and understanding before judging—which many avoid. The world is full of educated people missing simple logic and uneducated people full of wisdom. Common sense isn’t a school lesson; it’s a life lesson. Some skipped that class and never asked for notes.
I have a girlfriend who is extremely book smart and others has told me that she is an odd one. I don’t think so, she takes it all in before she replies. I think she is thinking even when she is walking. 🚶🏻♀️📚
I like her❣
Now, there are several humans that do lack common sense and lack being smart which sometimes it’s due to bad habits: drinking & smoking. You would think they get tired‼

Common sense is Rare because it is not common .
It requires thinking too,
So it’s not common