Why are market orders blocked for T2T stocks?

Market orders are blocked for T2T stocks because they are illiquid and have a wide bid-ask spread, which can lead to unfavorable execution prices and potential losses for investors. Blocking market orders protects investors by preventing them from being filled at prices far from the last traded price, which is especially risky in a T2T segment. Investors must use limit orders to have control over the execution price.