Honestly what were they thinking when they made TROS and The Mandalorian BOTH feature a new desert planet. At least making it Tatooine eliminates one of them.
I mean, aren’t desert planets more likely to exist? As sand is just tiny rocks?
That aside, the reason is because it evokes the imagery of A New Hope. Both were incredibly nostalgic, though in very different ways. That nostalgia is a big reason why though.
It’s also cheaper to shoot on a “desert” because there’s less likely to be any real world interference, and there are less set pieces to believably recreate (bringing trees into the Stagecraft set is harder than some sand…)