Being used server side JS since before NodeJS came along on JVM. I would say your assessment is correct (input validation) around that time. However React, Vue,

Being used server side JS since before NodeJS came along on JVM. I would say your assessment is correct (input validation) around that time. However React, Vue, Preact, Svelt, SolidJS (not to mention web components) changed that. We now have a group of people ONLY associated html rendering with those type of frameworks and components. So HTML rendering on the server side is pivoted to cater to those type of front end developer with 'Hydration'. The EJS templating type of rendering has being phased out. It is not good or bad, it is catering to what developers are use to.