When they are juvi's they tend to "taste" everything. Or at least mine did. They are also clumsey eaters. I had one get impacted because he got a mouthful of sand with each bite when chasing crickets. I lost that dragon. Also when they pooo if you don't get it all with the heat, lights, moisture (as beardies need moisture) you can cause the bacteria of the poo to spread and that in turn can cause illness.
It is much better to use a substrate that can be completely removed, cleaned, sterilized IMO. I personally prefer indoor/outdoor carpet and have several pieces that I rotate through the tank.. When its time for cleaning I can hose it down, use a little bleach and scrub and rince thoughouly and hang to dry. Put the swap out piece in the tank and leave the cleaned one for the next cycle.