Why use a React Framework such as Gatsby or Next?
Using a React framework speeds up the web development process by giving you an often single thing to type into the command line that takes care of the beginning stages most websites have in common. This includes your basic folder structure, Webpack, ESLint, babel.
gatsby new my-site-name
Many frameworks also include basic integration of plugins many people end up installing anyway, like Styled Components, Emotion, and CMS integration.
Anything that speeds up the web development process without cluttering up or bloating the installation is a hard yes for me.