"Nevertheless, I don't feel deprived nor advantaged by the knowledge of the existance of this key/ note."

Fine, maybe you don't need it.

As for the advantage aspect, if i gave you a screwdriver and told you it was useful, but you had never seen a screw, much less know what it does, you might think it useless.

If you were building something though that a nail could not accomplish, you might suddenly discover how useful screws are and then you might be inspired to discover the world of cross heads, flatheds, allen keys etc.

Seek and ye shall find.