You have to need it in case of:

• your website contains logins
• your website has forms that require personal or credit card information from your customers
• users chat on your websites

The SSL Certificate secures the personal information. It will make your users feel safer while making the online transactions, when they'll know that the website is secured by a trusted Certificate Authority.

If you have a blog or information website, I still recommend you to need an SSL certificate and a domain validated SSL is enough for startup website. By having an HTTPS link, your website will rank higher on Google and will be more trustworthy.

If you want good information on how to protect your website without bullshit, here's a blog with valuable information about it.

https://aboutssl.org/what-is-ssl-certificate