Google is pushing webmasters to move to SSL, Chrome 62 will be released in October and it will start to show warnings on non SSL sites with input forms and all non SSL sites browsing from incognito mode.
You can use SSL certificate with any site, no issue. Site and data on it become the secured due to the SSL service. When there is communication between the web hosting server and your website, for example, contact form that time, the data is used pass safely that is is encrypted form on the server due to SSL.
So there will be no in-between data hack due to SSL certificate. It provides the assurity to the user who is accessing it that the site is safe to access so visitors access it without any hassle. SSL used to provide the green padlock in the web browser which ensures that the site is safe to access.
So it's always recommended that you should have the SSL certificate on your website.
SSL certificate will be used to establish an encrypted connection between your web server and users' web browser. Certificate Authority (CA) validates your domain name and/or Organization to issue an SSL certificate. Once you SSL cert issued by trusted CA, you will require installing on your web server to secure connection to your website. It means SSL/TLS Certificate enables cryptographic protocols (e.g. HTTPS) that are used to encrypt all information transmitted over a computer network.
So, it doesn't matter web pages has vulnerable information is present or not. All information will be protected in transit with 256-bit encryption.