Because Etsy is not a general second-hand marketplace. Its niche is artisans making small batch items. And making your own thing at the scale of ebay is not exactly a small feat.
Etsy used to have strict limitations on what was allowed to be sold. I'm not sure how effective it was, but since that restriction has been removed, you're right, they'll list anything. Etsy has become a graveyard for dropshipped garbage, and the odd CD key, apparently! CD keys I can get behind.
