I think, at least in part, due to the loss of the knowledge base that ebay once had because there were once far more real enthusiasts and far fewer 'traders'.

I started collecting Art Deco glass at least 40 years ago, to begin with I didn't even know it was Art Deco, I just liked it.  Over the years I bought anything that took my fancy, it wasn't until I found ebay that I began taking any serious interest in the manufacturers and names/ numbers of pieces etc.  When I first started browsing ebay's Art Deco category it was a treasure trove of info. provided by sellers who knew far more than I and filled their ads. with lovingly written, accurate descriptions. 

I learned so much from them, including websites for I.D'ing and discussing glass.  That has mostly gone from ebay as has, all too often, any attempt at accuracy.  Search for a named glass maker and I get a motley collection of often wrongly ascribed, seeming guesswork and too often multiple choice names trying to game the search results, such as "Art Nouveau Art Deco Bagley Davidson Walther".

With one line descriptions telling me to "Look at the photos as they are part of the description" when, in fact they are all of the description (and often poorly shot at that).  Or worse still the execrable fluff and nonsense generated for the totally ignorant or lazy by A.I.  This sort of seller knows nothing and cares even less about what they're selling.  They probably genuinely believe that the "stunning and rare" item that they're trying to sell for £9.99 was made with random bits missing from the edges.