Market orders for long-dated options are typically blocked due to liquidity and risk management practices by the exchange or brokerage firm.
The lack of liquidity heavily influences long-dated options in market order. They also have lower trade volumes in comparison to their near-term counterparts. In an illiquid market spread, the execution price for a long-dated option can vary from the expected cost.
Additionally, brokers often restrict market orders for long-dated options and recommend using limit orders. They allow you to specify the option's maximum or minimum price, offering more control over the execution price.