Not only do winning players get quickly banned like sibling said, the house take on the major platforms is vastly higher than with traditional sports betting.
What kind of markets is this referring to?
Polymarket still charges 0 fees. While Kalshi's fees+spread can approach or even exceed traditional sportsbooks on some markets, neither of them have any interest in banning winning players, as they don't take a side on any bet and directly benefit from more betting activity. Kalshi also pays interest on bets, which can add up on longer term positions.
Betfair has operated with a similar model for decades in the UK and elsewhere.