I’m not sure why it’s any more unprofessional for pilots to be making credit card pitches (in flight, obviously, not during takeoff/landing/approach/anything even suggesting a sterile cockpit is appropriate) than it is for flight attendants to make credit card pitches.

I disagree. I appreciate it when pilots tell us about the route or interesting sights even though it’s not safety or operations-related, but I’m sure it causes some people to tune out. I’m not particularly good at recognizing the difference between a pilot’s voice and a flight attendant’s voice, except when I catch myself stereotyping male-sounding = pilot and female-sounding = flight attendant (and then scold myself for my prejudice, but I know I’m far from unique there). When there’s an emergency situation, the pilots are mainly using the PA to get the message to the cabin crew, who are responsible for amplifying it to ensure that the passengers get the message (eg “brace brace brace”). After that, it’s the pilots’ job to fly the plane and the cabin crew’s job to communicate the procedures they’ve trained for to passengers.

To be clear: I don’t like it when anyone uses the PA for credit card pitches. I just don’t think the pilots doing it at cruising altitude is any better or worse than the flight attendants.

Um, it’s entirely possible for both flight attendants and the pilot not flying to be there primarily for your safety and have plenty of time in a flight in which there are no safety-related tasks for them to do.