The thing about Mars specifically (compared to the Moon) is that it represents a much larger commitment. Long term human presence on Mars isn’t something that’s as whim-friendly as the Moon is: you either plan for being there long term (including some level of self-sufficiency) or you don’t go. At the same time, it’s a goal that is probably within closer grasp than building freely-moving, permanently spaceborne crafts that are large and advanced enough for continuous, long-term human inhabitation.

With that in mind, many view human settlement of Mars as something as an insurance policy against decades-long periods of stagnancy like we saw from the late 70s up through the 2010s. It’ll apply strong pressure on the parties involved to continue to improve the technologies involved in getting out there and back and living there in ways that a human presence on the Moon won’t (you can’t get away with a lightly modernized rehash of the Apollo missions; that’s not good enough).