I'm thinking because they couldn't burrow around in it, when it came time to clean the cage it would be really easy to do so, as you wouldn't have any surprises hidden down below...it would basically be on the surface. I'm thinking this is right. Right?? In my searching around on the net I read somewhere ( 1 article) that said when they try to burrow in the sand they damage their noses and faces to the point of bleeding in their determination to dig a burrow. By the sounds of your message you don't have that problem...basically on account of you giving them all that cardboard to munch/shred on. Correct??
it does NOT damage there noses and faces lol, 2 of my boys are allergic to all regular kinds of bedding so sand is all I can use. for digging I place a jar in their cage, they dig inthe jar not the sand. for cleaning I just use a strainer, sand falls through, poops and clumps from pee stay in the strainer, its really easy cleaning. 2 of my boys are going on 4 years old now, and they have never had a problem as a result of sand, and a healthy gerbils coat is very sleek so the sand slides right off

I have 1 solid agoutie male, 2 white spotted agouti females, a spotted black male and a mottled black male.
these are my 2 oldest boys, scriibles is the spotted black and doodles is the mottled black


this is Cinder, a solid agoutie male


here is one of my spotted agoutie girls, they are intentical exept that sniffles has a full tail and stubby came to me with only half a tail(defence mechinism the end of their tail comes off, so when you hold the tail you have to hold close to the body)