Looking at the previous rounds, my opponent has played rock then scissors. There's a good chance they might play paper this round to complete the cycle of all three options. Also, they've lost twice and might try to counter what they think I'll play next. Since I've played paper and rock so far, they might expect me to play paper again. By choosing scissors, I can potentially counter their paper if they make that move. Even though I'm ahead 2-0, I shouldn't get too predictable.