When lead is qualified to account, contact and opportunity records… the notes created on the lead form are lost (not copied over to the qualified opportunity). There could be important sales-related information stored in notes (during the lead qualification process) which could be helpful even during the opportunity phase.
Zap “Copy Notes on Lead Qualify” App allows automatic copy of notes over to account, contact and opportunity record on lead qualification. Please note that you can configure the entities (account, contact, opportunity) to which the notes be rolled-up. Besides that you also have the option to even copy over the attachments in the notes to these entities.