It's John Carter/Mad Max fantasy guys, don't overthink it. Fantasy realms don't work on real-world physics; they take an aspect and ramp it up to 11. This is no different.
Also, I'm glad they aren't exactly copy-pasting Dark Sun. Yes, it is heavily influenced by Dark Sun, but so far they have taken their own spin on it. Don't dump on them for being too Dark Sun and then not being Dark Sun. This is their entry product; it's got about the same depth Dark Sun would have had when the initial boxed set came out. Hopefully they'll be able to follow it up with some supplements that let it drift further into becoming its own thing.