Well that depends. Do you want good search engine rankings in Web 2.0? Because I think you do. Site maps are not just good for users, site maps, even on the page, even HTML site maps can also be a fantastic way to distribute page rank throughout your site. One of the best ways to test out how crawlable is your site is to click around within your site and see if you can reach every page.
Well if you’ve got an HTML site map, you’re pretty much guaranteed that you’re able to get to every page. There’s different ways to do them. If you have a ton of pages, maybe you want to break your site map down and maybe have it chronologically or alphabetically so you don’t have to have thousands of links all on one page.
In many cases you can find out, what are the top pages that I care about, or even if you don’t want to highlight every single page you can highlight the top-level categories on your site. So those are some of the factors to think about. I think it’s always useful to have an HTML site map.
On my blog for example, I have a sidebar with all the posts from each month going back all the way to like 2005 or whenever I started my blog. And that’s a very simple way that users can go back in time, and Googlebot can go back and find all of these individual posts as well.
Not to have only a XML site map that you submit to Google webmaster console. It’s very handy, it’s good usability, and it can be great for your search results.
by Matt Cutts - Google's Head of Search Quality Team