What is the deal with this minecraft key reward?

Yes all these referral sites are scams. You refer which gives them move people so that's 1 to them. After you get your required referral you then have to fill out a survey which will lead you no where. They get paid for these surveys giving them money to scam more and more people. Nothing is free in this world, everything requires money now. Only way to get an account for free is to get a friend or family member to buy you one.