For example the Kanye West account which was also hacked. The famous US musician is "tweeting" he will duplicate the Bitcoin sent to his Bitcoin address. With common logic, it is unlikely that anyone would give free money in the form of Bitcoin, without any veiled intentions.
No one will give you free money, not even Bill Gates. If it sounds too sweet, then it's certainly not true, especially in cyberspace.
It's a Bitcoin giveaway then why should they ask you to send money to their BTC address? that's absurd. Scammers kept on doing the same thing simply because there are people who still believe and fall into it which is why reporting/taking down such fraudulent bitcoin giveaways is the best solution for everyone. Remember this, there's no such thing as free bitcoin so always be logical and doubt everything you see on the internet.