Whenever something is given free, we need to know on what basis its been given. For example something is given as a compliment on some purchase it doesn't mean it is free. Indirectly we'll paying for it. Here the consumers are happy about the compliment while the seller is happy with added revenue. With bitcoin giveaway same is happening, the scammers just to make people happy term it a giveaway and the common users fall for it. Finally only the scammer feels happy.