NDT* does an excellent job explaining this every time he gets a chance to do so. One of my favorite quotes is him saying something to the affect of "take a look at the pioneers of space exploration. Note down their age. Notice a trend? They all grew up during the apollo programs! Why? Because sending a human to the moon was exciting. How many people do you see today with posters of the rockets that carried Perseverance or the rover itself versus Apollo or even the Shuttle? We must put people in space, not because the science demands it, but because of the impact it will have on society."
Sending humans to Mars isn't about exploring Mars. It's about the impact this would have on society as a whole. Suddenly, there's another planet out there that we care about and focus on. Perhaps wars on earth seem just that much more petty? At a minimum, it will likely inspire a whole new generation to explore the cosmos.
* Neil has his flaws, I get it, but I've sort of come 360 on him. His exuberance is contagious and as ambassador for space exploration, his approach does have a certain "public resonance" to it that I've not seen from others even if he tends to embellish things...