The core function of an SSL certificate is to protect server-client communication while dealing with sensitive data, such as ID's, passwords, and credit card numbers.
Back in 2014, Google announced that it was adding HTTPS as a ranking signal,serving your entire website over HTTPS also improves your SEO too.
SSL certificates are vital from the customer's trust point of view. The easy-to-identify signs inform the users that the data they send will be secured. .