Why do the soft skills matter?

If you invest time in the student teaching the soft skills, regardless of subject, then the student knows you care about him.

If the student knows you care about them, then the student cares more about your class.

If the student cares more about your class, then the student cares more about school.

If the student cares more about school, then the student is (more likely) wants to be at school.

If the student wants to be at school, then the student tries harder in their other classes.

If the student tries harder in their other classes, then the student's overall demeanor toward school becomes more positive.

If the student's overall demeanor toward school becomes more positive, then the student is a happier person.

If the student is a happier person, then the student tends to treat people with respect and appreciation.

If the student treats people with respect and appreciation, then the student becomes a better citizen.

Thus,

If you invest in the student teaching the soft skills, regardless of subject, then the student becomes a better citizen.