I think Basil got it just right.
In case of an issue a tech issue delaying departure that might be causing concern to nervous pax, a quick face to face by the Capt is an excellent idea. In fact, depending on circumstances, other types of delay might merit an appearance from the Capt, after all anyone familiar with CRM, something I doubt a number of posters on this thread are, will be aware of the importance of the visual element of communication.
As for standing on parade as the pax disembark, this isn't something I do as I'm usually still busy running the shutdown checklist or filling in the ever increasing amount of paperwork. If I do happen to be out of my seat, customer service and basic politeness dictates a quick goodbye is in order.