For example, ISPs are not able to crawl your traffic if it's via HTTPS. I've worked on data sets gathered by major ISPs and it's scary how much they know about their users (especially if they also have a mobile phone with the same company). ISPs use such intelligence for personalised marketing (either for their own product catalogue or 3rd parties)
The domain isn't, the full URL is. (But content size etc probably still allow identification of an individual page on a small site, and the context of the domain is already valuable)