I'm afraid I'm at work so I don't have access to printed sources, and I'm having trouble finding worthwhile sources online offhand (which actually might act as secondary evidence -- there are a lot of results for Apollos 8, 11, and 13 broadcasts, and not much for any of the other missions).

That being said, media attention and national/international interest in the Apollo program peaked with Apollo 11 and fairly rapidly dwindled, surging again only with the Apollo 13 near-disaster. Mid-flight broadcasts by Apollo crews back to Earth were no longer televised, requiring astronauts' families to come to Mission Control to see them.

"The whole world was glued to Apollo 11," said David R. Williams, planetary curation scientist at the NASA Goddard Space Flight Center in Greenbelt, Maryland. "But by the time they got to 16 and 17 the general public just really wasn't that interested anymore."

Coming at things the other way, Roger Launius argues, based on polling at the time, that the public never really cared much about going to the moon in the first place, so once the big milestones (orbiting the moon with Apollo 8 and landing on the moon with Apollo 11) passed, interest returned to its "background" level.

The Apollo program was originally planned to run out as far as Apollo 20, but the lack of interest (and concerns over the Apollo 13 mission's outcome) resulted in program cutbacks, making Apollo 17 the last manned flight to the moon to date. The remaining Apollo hardware was either put on display or repurposed for use in the Skylab and Apollo-Soyuz projects in the 70s.