It's an issue because on the CRJ, the cargo bay is in the back. On larger planes it's under the seats. So, if you have no luggage, the back of the plane is empty and the front weighs a lot more. So, either you make the plane back heavier, or the front lighter (ie shift pax back or offload).
The CRJ was apparently designed with the weight/balance point particularly "tippy" so there is a lot of moving around. The problem is lessened on the CR7 because it's bigger (hence weighs more to begin with). I've never had a w/b problem on anything other than a CRJ (or prop planes).

I don't think a CRJ-500 exists...does it?