1. SSL certificates encrypt the login details when they are submitted. Without this encryption, login areas can be vulnerable to attacks, such as man-in-the-middle attacks, and users could end up sending their credentials to the attacker by submitting them over an unsecured connection. As many people unfortunately use the same password for multiple areas, this can have enormous consequence.
2. Many people now fully expect login forms to be secured via SSL as it is a standard security practice. It puts users' minds at ease as they really should not be logging into any page that does not encrypt the credentials they submit.
3. Website security affects everyone. Google has now begun using HTTPS as a ranking signal, so any URL that is secured with an SSL certificate will be ranked higher than those that are not, including My Listing created through Listing Builder. Over time, Google may even increase the weight this carries in page ranking.