Steemmonsters: Why can not you play (rated) without a starter pack?

I bought a Summoner and some monsters in the trade and wanted to play Steemmonster.
However, I got the message when clicking on "Rated" that this is not possible without a starter pack.
The reason is that this is necessary to prevent multiple accounts.
Somehow, I do not understand how to prevent this, because anyone who pays $ 10 to buy a starter pack can play, and what's stopping him from doing it twice?
Besides, it is quite legal for Steemit to open several accounts if you pay the costs yourself.
So why not fight without starter pack, only with monsters from the trade (rated)?