If your website contains logins or web forms collecting personal information from customers or gets credit card information from customers, then you need to use an SSL certificate on your site. If you do not secure your site with an SSL, there is a sure chance that the data can be exposed to a third party and you lose the credibility of your website visitors.
Apart from that, Google Chrome 70 and later versions automatically mark HTTP sites ‘Not Secure’ when user uses any web form:
SSL certificates can also be used on web servers for Internet security and mail servers such as IMAP, POP3 and SMTP for mail collection/sending security.