Two or three years ago, it seemed like Delta was doing a pilot project of having the captain or first-officer come out of the cockpit and make his pre-departure flight announcement from the galley area. I know it had to have been a pilot project because for a while the post-flight surveys specifically asked about these interactions. All of this occurred on domestic flights -- JFK, DCA, DTW, SJU -- for several months on every flight. Also, the captain or first-officer was positioned next to the flight attendants on departure, thanking passengers for flying during deplaning. There were even a couple instances of the captain or first-officer walking the aisle in first-class and thanking those passengers seated up front.
Then it stopped. I haven't seen it since. I think the post-flight surveys still ask about it, but again I never see it.
As for flight attendants:
1) I would say about 10% of the time the purser on an international flight or flight leader on a domestic flight will personally thank all of the business-class/first-class passengers before landing using their name off the manifest.
2) About 90% of the time the purser on an international flight will personally thank passengers but not use the name or elite status.
3) On domestic flights, the flight leader will personally thank passengers but not use the name or elite status maybe 40-50% of the time.
I've seen handwritten thank-you notes from placed at every first-class seat in Honolulu and at every intra-Asia business-class seat in Guam before. Never anywhere else.