I've got friends who have lost so much money from trusting rewards and giveaways. Really not worth it unless it comes from a legitimate source; Blockchain.com, Coinbase or BAT rewards etc.
That's just greed, you must be talking about those scam ETH giveways on twitter. I strongly believe only greedy fools with mindset of earning quick & free money (Ponzi scheme business) fall for those type of Scam. From the name give-way they're supposed to understand it's meant to be free if it's truely a giveways and anything that involves putting xx amount of coins to get xxx amount in return is just pure Ponzi which means scam and should be avoided. Good they learnt their lesson though.