The bid price is the price a member of the public can get when selling an option. The ask price, which is higher, is the price an investor will have to pay when buying the option. Market-maker firms frequently can meet their expenses, and turn a handsome profit, while offering more modest spreads to traders on the floor. By offering better prices, they can draw business from professional investors who use floor brokers to negotiate better prices. The trading screens show the wider bid-ask spreads set by the specialists.
Floor traders can insist that specialists display their better prices on the trading screens.
But they don't. One reason is fear. But fear is not the only reason traders don't insist. And investors base their limit orders on the same artificially wide bid-ask spreads. One trader notes that the growth of automatic execution of trades means that more and more trading is at prices set by the specialists.