After the NSA scandal in the U.S. in 2014, Google has always pushed for websites to help protect their users' privacy. The best way to protect the privacy of your data is by using the HTTPS protocol (SSL certificates).
After first starting to prioritize secure websites in its search engine, Google strikes again with Google Chrome by warning its users when they visit a website that isn't using the HTTPS protocol. You will soon see a red X in your address bar to show you that the website isn't secure. You can see an example below:
If you add this to the decrease in performance of your SEO, having an SSL certificate on your website (to use the HTTPS protocol) isn't an option anymore, it's pretty much an essential part of your website.