How many times have you had to do a search for a term paper or a PowerPoint presentation and looking for some particular photo without having to learn how. Most geeks would recommend in these cases certainly use the service that Google Images based on targeted keywords can get results more or less satisfactory.
Leaving aside the question of copyrights on the images that recall can not be freely used without permission. The practical problem is therefore to have to enter any site and save the original image, which certainly requires some time.
