It's not a giveaway for everybody. Let's say it's a competition or a chance bet. Users who are eligible to participate would have to retweet the status mentioned above and wait for a chance to be picked up. I don't know the basis of winners selection but i have just this tweet reply from coinmetro official : https://mobile.twitter.com/CoinMetro/status/1226253296995840006
They also set a signup bonus for new registrants.