Prediction markets Kalshi and Polymarket claim to be truth machines that offer insights into everything from elections to interest rates. But they are also something else: Massive sports betting platforms. Recent reports have found that sports wagers accounted for over 85% of all bets on Kalshi and that, during one four-day stretch, the platform made $25 million in fee revenue from March Madness alone. Prediction markets may have all sorts of pr…