The wager requirements for free boxes would have been a good decision if Betfury had kept everything as it was. However, Betfury decided otherwise, and it seems that free boxes only for rank 2 users and above are a more optimal solution for them in the fight against abusers. Even if we assume that some abusers can reach rank 2, there will be only a few such abusers of their total number, which means they can easily be detected and blocked by Betfury.
Wagering requirements would indeed also be a good idea. Since the beginning, the boxes were able for level 1 but initially the rewards were a lot higher and more interesting. They kept dropping the amount you got collect but guess it didn't really help to weed out the abusers so there are now taking extra steps by making it only available for rank 2 and upwards.