It's also true for moving a web from a host to your local machine and from a server to a disk or another folder on your hard drive. Lots of folks try to use the Import feature for this. It seems like a logical approach, but the Import feature was not designed for this. True, it can move all the linked html files and images in a site. That's not all there is to a Web site, however.
Import follows hyperlinks and image paths to find the files it takes.
It can't find a form handler. It can't follow a JavaScript redirect. It can't find a FrontPage theme. Import is for bringing individual files or small groups of files into your site. I have also used it to suck in all the images from a client's existing Web site so that I have all the pictures I need for a redesign.