That’s neither simple nor a fact. Space exploration has almost all been robots, telescopes, probes, etc. The interest has been self-sustaining with an endless stream of discoveries, discoveries including still Voyager.
And the average person has almost no interest in it, except for world-history events like the first landing on the Moon. The first landing on Mars would be a similar event.
Sustained funding for 60 years shows the continued interest in there, to use one of the “reasons” you cite for Apollo.