This is one of my reasons. I also believe that compared to the Moon, Mars is more likely to both give crewed spaceflight and human habitation of other bodies the big boost it needs and make it more of a permanent fixture — the Moon’s relative convenience is a problem in that it makes it just as easy to mothball as it is to get to. Lingering too long on the Moon as the focal point brings substantial risk of backsliding into Shuttle-era stagnation.
It’s a result of the much higher level of commitment required to undertake crewed Mars missions. You can’t lean on Earth being nearby and contingencies have to include e.g. uncrewed resupply missions failing… it’s the sort of thing you have to go all-in on, after which pulling out is costly and looks stupid.
By contrast, backing out of the moon is comparatively trivial. At worst it’d take a couple weeks and the expenses quickly lost in the noise.
With Mars, there’s also the possibility of a “Wild West” element once things are established enough where groups of people simply refuse to return and cutting off support from them would have really bad optics.