"Listen, here's the thing. If you can't spot the sucker in your first half hour at the table, then you ARE the sucker." The first lesson of Rounders, one that we learn in a matter of minutes, is that everyone is a mark. Everyone can be manipulated and taken advantage of, and if you're not willing to acknowledge that, then you're the one who is going to be walked all over. This opening immediately puts us in the head space of the characters, the sort of kill or be killed mentality they all have at the card table.