Why do otherwise intelligent speakers insist on disgorging every bit of their wisdom in every speech?

A speechwriter was grousing to me this week about a client who wants to pack eight points into a commencement speech.

“Speakers feel the need to disgorge every last bit of their wisdom in every speech,” came my words, simultaneous with the insight itself, “because they secretly hope every speech is the last one they’ll ever have to give.”

Might I be onto something? —DM