Since the beginning of 2017, Google is trying to force every website to adopt the “https” (HyperText Transfer Protocol Secure) mode. It has become more obvious from October 1st, 2017, with the new version of Chrome 62.
With this version, any internet user going on a website with the http protocol, can see a warning message NOT SECURE appearing on the webpage and not only on the url bar.
As 75 % of the internauts use Gogle Chrome, there is a risk if your website is not yet on the https mode, to see them avoid it, because of the warning message.