The system is in place because of the following example:
Person X makes account (reffered to as orig).
Person X makes alternate accounts (alts).
Person X has alts play and get low cost cards
Person X has alts trade all but low cost cards to orig
Person X uses cards to improve deck/sells for clintz
Person X makes profit.
With enough people doing that, the company who runs this would need to shut this game down.