In recent years it seems like this site has become flooded low-res, lossy quality, censored, or incomplete works that essentially function as advertisements for an artist's paid service.
I don't plan to ever use a paysite and I don't come here to essentially get advertised to.
I think it makes sense to make a tag for these promotional pieces so that users like me don't have to see them and get disappointed by half the thumbnails that we open.
Conversely, a user who has already resolved to spend their money on art can also search by the tag, too, so it's a win-win.