Can't speak for everyone ofc, but not sure if I ever wanted blurry placeholders when images load fast enough, or found them anything but annoying when not. I think these bells and whistles only serve as designer's self-affirmation.
Agreed, they just create needless visual activity. How about a page specify where the images appear, and leave it up to the browser to decide how to show them and load them? Is that too simple and workable?
I've definitely wanted them on photo galleries with large numbers of thumbnails, and I appreciate them when they are implemented well, especially if I'm on a slow connection.