I think it is also to drive home the point that these are as-is where-is. No return, no exchange, no warranty, no kidding. I don't sell on ebay at all but understand from others that dispute resolution is tilted heavily in the buyers favor. So, the seller wants to be extra clear in their listings so there can't be any dispute by the buyer later on about just what was on offer.
Of course, non-tech sellers probably often make the mistake of damaging a vintage unit by just plugging it in with no variac, then see the magic smoke and realize they screwed the pooch.
Kevin