HTTPS is an encrypted method of data transfer that blocks virtual eavesdroppers from seeing and using your information.
Technically speaking, unless your website is transferring passwords, payment information, or other sensitive data, there's no need for your website to be served over HTTPS.
But for best practices, and taking into account that HTTPS is a search ranking signal for Google, all websites should implement HTTPS across all pages.
"We've seen positive results, so we're starting to use HTTPS as a ranking signal. For now it's only a very lightweight signal — affecting fewer than 1% of global queries, and carrying less weight than other signals such as high-quality content — while we give webmasters time to switch to HTTPS. But over time, we may decide to strengthen it, because we’d like to encourage all website owners to switch from HTTP to HTTPS to keep everyone safe on the web." - Google Webmaster Central Blog
So while HTTPS is currently a minor ranking signal, it's anticipated to grow in importance along with the Chrome implementation of the "Not secure" tag. While that tag itself is not a ranking signal, it would come as no surprise that the words "Not secure" being shown right next to your web address will certainly increase your Bounce Rate, decrease your Click-Through Rate, and diminish the overall level of trust that users find in your website.
BnBwebsites strongly recommends that all website owners begin adopting HTTPS now before it becomes a much more important Google search ranking signal, as it's becoming an essential part of a well-designed, fast, and user-friendly website.