The dealer can buy a special disk from the software house that can be activated by a licence key. He then contacts the manufacturer who gives him the key which works for the number of times he bought. When he has used up the key, it is reactivated on payment of another fee and so on. That way he can install the software many times using the one disk. That's why you don't get disks with pre-loaded software.
The only way you can get the discs is to buy the software yourself and have the shop load it for you.