I don't think that saves bandwidth, since the same pictures are from the same URLs. They will just be shown repetitively, but won't affect bandwidth. Correct me if I'm wrong about this.
Saving bandwidth or not, the more important thing is that it's annoying to see the string of images over and over again on the same page, so this implementation is a good idea. But it really boils down to each forumers' ethics, imo, because quoted posts can still be edited at will so forumers can decide whether or not they want to exclude the images. It's just that this feature will automatically do so to make things easier.
The point being, this wouldn't be needed if we are responsible enough to exclude the images ourselves when quoting, yet there are those (whether noobs or not) who do quote the whole thing, making the feature necessary.
Though it is acceptable to quote one or two images that are not too lengthy/large in nature. :D