Here's what might be an illuminating experiment: search on 'stamps of Bohemia' and 'stamps of France'.
Both areas produce beautiful crystal, but one (probably) has zillions of listings for its postage stamps, and the other, well, less than zillions.
Q/ In which case does
ebay fill-out the search results with crystal wine goblets?
Why? One reason is the cornucopia effect: every site visitor should always be forcibly imprinted with the impression that there is lots & lots of stuff you can buy on
ebay.
Another is that there is no reason to expect that every site visitor actually knows what they want.
The motivated, particular visitor can search within the results or, better, scroll past the 'keyword cousins' to find what they really want. The others? I've never been to
ebay HQ, but I could imagine company coffee mugs bearing 'scrollers are buyers'.
Put another way: can you honestly say that you have never clicked on a serendipitous search result?
Cheers,
/s/ ikeyPikey