I guess you know the answer, and it has been mentioned several times already: search is "bad" from the seller's point of view, they don't want you to buy what you want. Instead they want you to buy what they want to sell, and that is of course easier if they control the presentation of products. Search is an explicit way of trying to give control over what is shown to the user, and that runs counter to the underlying optimization for maximum sales.
At least I guess so, the nearest I have been to any kind of sales optimization pipeline is buying a lot of stuff online. :)
Smaller and niche sites can still do Real Search, but it's the large marketplaces with thousands of everything (where, you know, you really want good search) that usually instead favor their own optimization.
Actually, but perhaps surprisingly, a site like Aliexpress actually kind of explain this in their search help text, which is at least trying to be transparent. I like that, but it still drives me nuts when the search results change when you change to sort by price. That's like ... "impossible" in my mind; changing the presentation order of a list should not change the contents o of the list, but there you are.
Aargh, basically. I wish it could stop.
Applying Standard Capitalist Rules, I guess in the future you'll need to pay a fee to each site for the right to search and sort exactly and disable the optimizations for you. Fun times.
EDIT: Minor grammar fix.