Why do you think SSL/HTTPS is important?
It's imperative that websites and their operators have taken all of the necessary steps to ensure that the integrity of user data is maintained. Similarly, a website must ensure that it is protected from being defaced or hacked. HTTPS uses encryption provided by the Transport Layer Security protocol to ensure that data isn't manipulated whilst it's on it way to, or from, you.
HTTP, the precursor to HTTPS, is more prone to SQL injection and cross-site scripting.
In human speak, when visiting a site over HTTP, your credentials (i.e. card information, passwords) and/or the content on the website that you're visiting is more likely to be intercepted, stolen or altered when compared to HTTPS.
Additionally, Google favours HTTPS websites and has done since 2014. Therefore, secure sites are more likely to appear towards the top of search queries.
Today, there's no excuse to not use HTTPS. Vendors such as Netlify and GitHub Pages offer HTTPS encryption as standard. Let's Encrypt also offer free SSL certificates.
Supplementary information provided by Ricky Publico at GlobalSign.