[tjpnz]

To make Mars habitation sustainable you're going to need to launch hundreds of Starships every launch window. Some have speculated that it will take as many as 40 launches to fuel one Starship in orbit. The launch window lasts approximately 780 days so ~5 launches per day just for refueling - if something goes wrong you lose months.

For the moon you still have the refueling problem but you don't need to ship nearly as much to make a moon presence sustainable. You're not constrained by launch windows and there will be multiple providers able to plug shortfalls in the coming decades (I'm not sure the same can be said about Mars).