You need custom tools for React, too. Because JSX is not valid JS.
In most (all?) IDEs you can also tell the IDE to treat the file with a certain extension as written in any language
In most (all?) IDEs you can also tell the IDE to treat the file with a certain extension as written in any language
/ and < in operator positions becomes operators, whilst / in plain JS in a value position becomes the start of an reg-exp and < becomes the start of an JSX tag, so to handle it there needs to be a full parser (with a pull-lexer to correctly handle the contextual part) as you cannot just do a textual replacement due to ambiguity.
You can use .vue files, use JSX or write the h-function invocations by hand. Except for SFC-support, this also works without a build step: https://vuejs.org/guide/quick-start.html#using-vue-from-cdn
And what does this have to do with the fact that the absolute vast majority of react code is written with JSX and that you need special tools in IDEs to deal with React code (because regular JS tools would break)?