Since Google has indicated that it is going to reward secure websites with better search results, having such an https website has become even more important. But a better Google result is not the only reason.
A secure website, which you can recognize by the https prefix, ensures that the information visitors leave behind is sent encrypted. This way, it cannot be intercepted by malicious parties.
A secure website is also displayed differently in the browser's menu bar than an insecure website. So the visitors to your website are shown whether they can leave their data on your site with confidence. It shows the visitors that the company associated with this website is responsible and professional. Thus, the security of the website reflects on the reliability of the company behind it.