Scammers don't need this to copy an existing website, and I could see plenty of legitimate uses. Maybe you're redoing the website but want to keep the previous site around somewhere, or you want an easy way to archive a site for future reference. Maybe you're tired of paying for some hosted CMS but you want to keep the content.
The website in question may be a dynamic website (e.g., WordPress, MediaWiki, or whatever other CMS or custom web app) and you either want a snapshot of it for backup, or you run it locally and want un static copy to host it elsewhere that only support static files.