SEO has moved on over the years, so do you feel that it's still necessary to include a sitemap page on a site (For UX purposes, as well as SEO)?
I vote no for UX and yes for SEO (with a caveat).
If your site requires a sitemap for a user to find their way around, then that's a smell that you have a poor information architecture. I don't buy the argument that they support users who know what they are looking for - like an index in a book. A website and book are sufficiently different that the comparison isn't useful. Use search if you need the user to find one piece of content from within volumes of it (think Amazon or Wikipedia).
The SEO story is different. A sitemap can help in that circumstance, especially if some content isn't accessible through normal user flows. The caveat is that using a sitemap XML file is probably more effective and doesn't bear the burdon of needing to be digestible by an end user.
Site maps are still useful in the same way that an index is still useful in a book that has a table of contents. It provides a different way of organizing information. A great website will naturally lead the users to where they want to go normally, particularly if they don't know exactly what they are looking for, but a site map is invaluable for quickly finding one particular thing that might be an uncommon activity. It's also similar to how automated phone systems are great for helping direct a large portion of calls, but when a caller can't be helped by that system, you still need a way to get to a person that can look at the actual directory and send them to the right people.