but people who are intent to steal their images are going to do it anyway.
Except it's not stealing, is it? Nothing is being taken. The people are just using the image for their own purpose with the idea being the image is still attributed to Getty, the distributor, and the photographer, who doesn't get paid for the use of their work.
Obviously at some point the person would return the image since they're just borrowing it, not stealing it. That's what happens when someone "shares" their music with someone else, right? They let the other person borrow the music and when done, the person returns the music back to the person who bought the cd/album/mp3/whatever, not keeping a copy for themselves.