I wouldn't say that such giveaways goes against spirit of Games and rounds board. I guess that if there would be requirement to make on-chain payments directly to BTC address, instead of paying it to casino ballance, then this board would be more or less dead. So, I rather would have such giveaways as we have now than no giveaways.
Giveaway participants will get benefits if they win - the casino also gets benefits, so both parties benefit. There is no problem with how they do it - if we don't like it then we don't have to enter their event. Maybe that's why not all users participate in the event. However, we can notice that many users on that board are very eager to get prize either in on-chain payments or credited to casino accounts.
