I don't exactly don't get it, do you have a link to this kind of source? so we are also aware of this and all of us here?
You said that they are sending a private key, but do you also know the address? We cannot open an account even if that is only a private key if we don't have the address, and double check what you are joining especially with airdrops, once they want to get your private keys then don't join automatically and tell it straight to the admin they will immediately make some action of those scammers.
Actually, opening a wallet through private key don't require an address. That's why, there is no reason for a person to share his/ her private key if it will be a disadvantage for him/her. However, I agree with your last statement. There will be no scammer if people will be informed.