He will not buy BTC from an exchange because he is seeking scam. If there is money to be made, scammers will hang around trying to find ways to exploit the situation. If the scam is presented again and again, eventually when it becomes normalised there will be gullible members falling victim.
There are ignorant people out there that are dumb enough to fall for this.
Why wouldn't the user just buy btc from an exchange unless they were just looking to scam or steal from someone? Smart people think about that and the not so smart get scammed.
Not sure why people in the world have to be so ugly, but unfortunately there's always bad people out there. Stay safe everyone and don't fall victim to this type of scam.