Do you remember the days when all of the sudden Google implied that all websites need to be mobile friendly?
Guess what. As per Google, a secure website. i.e an SSL certificate is an important component in keeping the search engines and your customers happy.
Why does this matter?
Simply put, your customers want to know they are in safe hands - an SSL certificate aids in doing just that by keeping data private.
The same with a mobile friendly website, your customer wants to surf through a website that is easy - a mobile website aids in doing just that.
Google priorities all of this because their sole interest is a happy customer. That is their customers find what they want and the data delivered is reliable.
That means the website is of high value, well known, secure and built for a mobile device.