The state of HTTPS in 2018: Why should you migrate?

People rarely take SEO recommendations seriously, especially when there are no direct repercussions of not following them. So, when in 2014 Google recommended that all websites should migrate to HTTPS, few website owners took it as a direct instruction. Fast-forward to 2018, however, and things are looking very different. So what is the state of HTTPS in 2018, and why should you migrate?