The Kroks who live Krokotopia like to live in the desert. Why you ask? Well, that's just how the people made the game. The sandiness also represents that it's the Balance world. That's the best I can explain it. Hope this helped!
Real kroks here do live in moist places, but remember, wizard101 is magical. Anything could happen! Krok is like the balance world, which is obvious since the balance school and tree are located there. Krok is so cool i would replay it anyday