This was added after the fact; to my knowledge it never told you to sell them. Ergo it was *added*, deliberate.
Yeah, so probably some intern was assigned "Stick this text on everything with no use" and did it... not noticing if the item has any actual sale value or not.
I sell everything with zero value to vendors, even though I get no gold in return, because it's easier/faster to 'sell' it all by double clicking quickly than it is to delete them one stack at a time.
I took the icon as a hint to do that more than as an indication of the devs trolling us.
The problem with society these days is that no one drinks from the skulls of their enemies anymore.