That reason is their overly reacting in the name of reality. WGT is giving this as an excuse in the hope that players will buy into that what sounds plausible. They certainly know this is only a game where reality isn't necessary. They are using this explanation as a cover for the real reason, which is to make money. If these balls weren't taken out of the game or lost you'd not spend money for their replacement. They are somewhat justified in this practice because the game is free, and someone has to pay for the upkeep of the game. My problem with what they are doing is why can't they be up front and be truthfull. while the practice may be justified the game is not free. To be fair here though, the game is free if one chooses to use the starter balls exclusively. Like I said earlier my objection is their duplicity in informing the consumer.
I've read on and find a vast number of players have legitimate complaints about an array of problems in addition to the one addressed here, although most are off shoots, either directly or indirectly for the the money needllessly being spent, because WGT ignores the complaints seemingly. Here again their reason is clear; WGT is the only game in town.