While we may all have differing views on this (and I would agree that by definition an "antique" should be at least 100 years old) the OP is talking about eBay. I don't know where tools are generally listed but if you check eBay Antiques category, you will see that one of the sub-categories is Art Deco (1925-1940), so eBay's definition of an "antique" is pre 1940.
Then there may simply not be an appropriate category for eBay listing, especially on Oz eBay where we have FAR fewer listing categories than other eBay sites. One I constantly mention is Sterling Silver. Apart from the Jewellery section, there is no specific category to list Sterling Silver, Silverplate or Other Silver than in the Antiques category. For this reason you will find completely modern "pre-owned" Sterling Silver items - like cutlery, spoons, napkin rings, decorative items - in the Antique category because there is simply no other separate listing category for "sterling silver" items.
To me personally the term "old" as a definition would be meaningless. To a 12 year old, anyone over 30 is old, while to me 60 seems quite young! I think as a descriptive adjective it's fine, but it would mean different things to different people. We continually have discussions about "vintage" - to me, it's anything that would have been made for an earlier generation, so anything older than 25-30 years. However on eBay it does seem to have become a generic term for anything that is second hand. "Classic" to me refers to style / design, rather than age.
As for plastic, bakelite was invented in the early 1900's, and the explosion in the mass production of plastic items in the 1950's following WW2 would certainly mean that there could be plastic handled tools well old enough for me to consider them vintage.
However I understand your annoyance - there are certainly plenty of things on eBay that annoy me. However we keep buying / selling / looking here, because at the moment it's still the best game in town.
