It is possible that the technique was not deliberately designed, but it evolved as a particularly successful result in scamming that was then replicated. Maybe

It is possible that the technique was not deliberately designed, but it evolved as a particularly successful result in scamming that was then replicated. Maybe the scammers thought "I have tried 50 different mails, and this is the one that got me incredible results"; so this was the one that was popularized, even if the people doing it didn't understand why it worked better than the others.