Social bookmarking have 4 best benefits.
1: Social bookmarking site provides social signals for SEO.
2: Many social bookmarking sites out there provide do-follow and no-follow backlinks to their users on every submit. Which is really useful for any website.
3: Social bookmarking provides the most popular platforms such as Reddit, StumbleUpon and flipboard, which are the most famous source of big traffic.
4: Increase website credibility: Many social bookmarking sites on internet are having very high authority. That will surely help you to improve your site authority such as page rank, domain authority, page authority and Alexa rank of your sites.