Google made an unmistakable announcement back in 2014 that it would start factoring SSL/TLS into its ranking algorithm. While the impact was fairly minimal at first, the positive effect an SSL certificate has on search results has continued to increase as the community pushes all sites towards encryption.
Websites with SSL are now experiencing as much as a 5% increase in search visibility compared to sites still only using HTTP. Also, referrer data is always preserved and much improved over HTTPS. This allows for greater keyword analytics and analysis for where a site's traffic is coming from.