A contextual clue may exist but be too weak for safe reliance. The speaker may therefore name the subject as a precaution. Mention can also compensate for an inattentive listener or make a previously established point more explicit.
Example: If several students are present, “Succeeded” leaves the referent uncertain, while “Zayd succeeded” identifies him. If Zayd is already in discussion, repeating his name can strengthen the point rather than introduce a new person.
The text distinguishes precaution against ambiguity, alerting the hearer, and additional clarification or confirmation. These purposes should not be reduced to a single rule that explicit speech is always more emphatic.