Not only is this randomly-resizing dialog box visually annoying, it turns what should be a super-fast process into one that takes a ridiculous amount of time. The end result is that users think they have a slow machine—”it took over 12 seconds to expand 25 tiny little archives!”—when what they really have is a horrendously slow GUI interface to a super fast task.
It took just 0.013 seconds with gzip Terminal.
Update (2016-12-09): Nick Heer:
[…] many archives will take less than a second to expand using the Terminal. Those files should, ideally, be unarchived in place, without opening an additional window.