Because you know that if you ask a scammer if they are scamming they are going to be completely honest with you and reveal that indeed it is all one big scam.
Actually...they sometimes do. The most insidious kind of scam in the scamworld is where the scammer pulls you aside and says in private, "Now kid, there's going to be a lot of flim-flam with this deal but I'll make sure you're taken care of."
If you ever hear or read something like this, a big loud siren should go off in your head.
A minor variant is the one where the scammer pulls you aside and, in private, says: "Kid, I like you so I'll arrange a special side-treat on terms you'll absolutely love. Just remember to stick by me when the time is right."
In the con artist world, con-man genius consists of making the mark feel (and even act) like he's part of the scam. That maneuver shuts up a lot of would-be complainants, perhaps all of them.
Be cool...ye hast been warned.