Before we begin, I want to say two things.
Yes, sometimes upon switching to HTTPS/SSL security on your website, you will experience a drop in rankings.
Yes, you absolutely, 100% should implement SSL on at least part of your site.
I understand that a ranking drop can be bad. I also understand that not all sites absolutely need SSL for their site. However, if you have absolutely any reason for a user to input any personal information, including just an email opt-in form, you absolutely should be using SSL.
The Benefits of SSL
SSL has a lot of benefits for a website. For one thing, Google has been considering SSL to be a ranking factor since 2014. It’s been a minor factor – a site with good content will outrank a similar site with poor content and SSL – but it’s a very real boost if you have it implemented.
SSL also encrypts information sent to and from your website. It can only be read and understood by the people accessing your site directly. No one can initiate a man-in-the-middle attack.
That old “don’t use the internet from Starbucks, anyone can snoop your traffic” concern is alleviated; if they were to intercept your traffic, all they would get…