Why Do Options with Longer Time to Expiration Often Have Wider Bid-Offer Spreads?

Options with a longer time to expiration (longer-dated options) have a higher level of uncertainty regarding the underlying asset's price movement. This increased time-related risk, known as 'Theta' risk, makes it harder for market makers to accurately price and hedge the contract.

To account for this greater uncertainty and inventory risk, they quote a wider bid-offer spread.