You don't need to get close to that level of complexity for React to become useful. > Meanwhile I have seen SO MANY sites that use full React for a contact for

You don't need to get close to that level of complexity for React to become useful. > Meanwhile I have seen SO MANY sites that use full React for a contact form with two fields on it. I agree that the contact form you describe would be dead-easy to do vanilla. Maybe throw in Parcel if you want to write ES6. However, while I suspect some people may use React in this case because it's all they know, others may do it because they are literally faster in React - they have a workflow that can see them code and deploy such a website to Netlify or Heroku or whatever in 10 minutes.