Why? I’m glad you asked.
Silly me. What was I thinking? That I might be able to read the labels on the diagram?
It isn’t bad enough that I have to put up with that crap just to upload a picture to this site. Add to that the fact that it’s overdone, cliché and a waste of bandwidth.
It was passé four years ago, and it’s definitely not new or innovative. It slows things down, gets in the way, makes it difficult to maneuver and as you can see, defeats its own purpose if the screen dimensions don’t accomodate it.
Oh, and if you trap a login in that lightbox effect, I will officially never use your site, your service or your product, ever ever again, for as long as I live.