Even if haggling is fun for you, it is still a big expenditure of time and effort that accomplishes nothing. There's simply no reason for it to exist.
A market vendor who knows an apple should cost $2 but charges $5 in the hopes of screwing over a tourist is just an asshole. I can't imagine how that builds relationships.
That is what's frustrating about negotiating for commodities like food. The seller is taking advantage of information asymmetry. They know what the standard price is, and they hope that you don't. It's scummy.
It is different when there isn't a set price, i.e. if you are trying to buy a one of a kind item. In that case even in the Western world some negotiation would be acceptable, (buying an original painting from an artist, for example). But this does not justify having to haggle for everything you want to buy, every time.
While I generally agree with you, if you're buying fresh food at a market, such as the apples in your example, it isn't necessarily a commodity. Quality and size will vary from one item to the next; why must they all be the same price? Places where goods tend to be more standardized seem to rely less on haggling and more on sorting: you don't haggle over the price of an apple out of a mixed lot, you pay a set price for a certain grade of apple which has been separated out in advance.
Even a published price is nothing more than a free option for buyers. It’s a ceiling. There’s nothing that prevents the seller from offering a lower unpublished price.
It doesn't take that long either. There are positives even to things you deem useless.
I don't get this one.
I also hate haggling, and since I’m not from a culture where it’s a norm I can’t use it to read deeper into a person. (Or them into me.) But it’s not too hard to imagine how it helps to build relationships.