While it's true in the wild they are out on dirt, it's not the same as what you're thinking. The sand that is found in most viv's is more like a dessert/Sahara style, not the hard pack of the outback, as Destiny pointed out.
Honestly to me it's just not worth it. When Sarth was just little, I put flag stones (not symmetrical) in his viv and filled in the gaps with play sand. I kept his food dish on a couple stones I had stacked so it was up away from any of the sand. Despite that though I gave him a
bath when I noticed he hadn't pooed in awhile, and when he pooed in the
bath, a bunch of small stones and dirt came out with, and he nearly collapsed from the effort of passing that. After that, I got rid of the sand. When I got his 4x2x2 custom tank, I went to Home Depot and bough a half dozen beautiful flag stone tiles. They weren't expensive and they trimmed them for me for free. They look awesome, and so easy to clean.