They are asking for users verification paying $25, so, they shouldn't call it a giveaway. If they want to give money to their users, then ok, make a giveaway, but if they want to pay for their users' verification, then don't call it a giveaway because that's only a bait and not a true giveaway.
It's how marketing works, everywhere. Free money doesn't exist, people should understand that by now.
The main point is that most people using blockchain or any other service, are not using it to ever spend money. What's the best way to increase the odds of having them become a potential paid customer? Right, offer them a giveaway in form of whatever crypto currency, and in return for that people 'only' have to verify themselves.
By verifying yourself you basically take away a massive obstacle that stands between you and the exchange. Now you can participate in future giveaways, and more importantly, buy coins instantly and use other services that involve fees, which is what they want you to do the most because that allows them to make money. Business are here to make money, blockchain too.