One of the problems in Argentina's elections is that volunteers of political parties steal the ballots of smaller parties from the voting room, and since these small parties don't have the man power or monetary resources to restock the ballots, they lose votes. A better solution would be single paper ballot, but the ruling parties don't want this because they are who benefit for the current system.
That said, this system prevents chain voting (a mechanism to make sure the votes that parties buy from low-income people are not changed).