I get what you are saying, there is no need to risk tc if there is no tc to be gained. However, when confronted with this suggestion I believe most staff members see it as this:
Bet on Person A > Multiple counters on Person B > Person A wins > Win my bet
Bet on Person A > Multiple counters on Person B > Person B wins > Lost my bet
Bet on Person A > No counters on Person B > Person A wins > Win my bet
Bet on Person A > No counters on Person B > Person B wins > Lost my bet
Either way, counters or no counters, whoever you bet on either wins or loses. If you made a correct bet, you get your tc. If you made an incorrect bet, you lose your tc.