They're haggling in disguise so that people can get away with the verminous practice in broad delight despite taking place in a society founded on decent and fair conduct. Here's why that matters.
Fair conduct means that one rule applies to everyone, as per the situational stipulations of the rules. There are no double standards, and law makers and enforcers do not have fiat. This is reflected in many aspects of civilisation such as shops having set prices. Everyone who walks into a Tesco or 7-11 and buys a sandwich pays the same price as anyone else does. Sandwich prices can vary based on circumstances, such as corner stores charging more or price changes over a long term, but ultimately a sandwich is a sandwich.
Haggling predates the fixed price shop, being a more primitive system. Primitivity means that less coordination or cooperation is needed to create a system, making it more robust for situations in which parties do not trust each other. Two enemies can be made to get along via haggling over a price for instance. But for a higher civilisation it is a primitivity that actively hurts trust. For any given buyer, there is the dangerous possibility that the seller is a ripoff merchant who's trying to overcharge you for junk. And for every buyer, there's a seller who's worried his customer is a cheapskate trying to undersell his valuables. Both are motivated to behave in a low and nasty fashion to try and ward off the prospect of being taken for a mark. And in practice, when everyone is forced into defensive savagery, everyone suffers. No trust, no cooperation, no higher civilisation. It's the proverbial "reason we can't have nice things".
When you study the stock market, it's all essentially the insidious return of haggling in a newer, more powerful format. The essence is attempting to buy stocks low and sell them high. This is dependent on identifying that a stock is going to be seen as valuable soon, so that it will be high for good selling.