About renewing your subscription

Why do Norton allow a non - admin user to enter a new subscripton key in NIS 2012 ?? , surely someone could enter a used key and totally mess your product up , and then you would have lost your current subscrition .

I have noticed this at work as i can bring up the Norton application , so in theory i could apply a used key and bring down their protection .   I wouldn't do this but i am just stating a weakness