Regarding your first point: you can place an item into the public domain but retain the copyright. See some of the Creative-Commons licenses that allow free use but disallow commercial use of your IP.
Regarding your second point: Getty is a content distributor. When it comes to stock photos, many designers just go straight to Getty or one of its large competitors to browse for stock photos. The designers aren't going to know which of those photos are available freely and which are not. (By analogy, this is why you when you want to watch a movie, you immediately find it to rent on iTunes, as opposed to spending twenty minutes finding a decent pirated copy.)
> Regarding your first point: you can place an item into the public domain but retain the copyright. See some of the Creative-Commons licenses that allow free use but disallow commercial use of your IP.
That's not what public domain means.
> The term “public domain” refers to creative materials that are not protected by intellectual property laws such as copyright, trademark, or patent laws.
> Works in the public domain are those whose exclusive intellectual property rights have expired, have been forfeited, or are inapplicable...The term is not normally applied to situations where the creator of a work retains residual rights, in which case use of the work is referred to as "under license" or "with permission".
Regarding your second point: Getty is a content distributor. When it comes to stock photos, many designers just go straight to Getty or one of its large competitors to browse for stock photos. The designers aren't going to know which of those photos are available freely and which are not. (By analogy, this is why you when you want to watch a movie, you immediately find it to rent on iTunes, as opposed to spending twenty minutes finding a decent pirated copy.)