Even simple single-file use cases may benefit from ESM support for top-level await. I thought I had heard of a proposal for supporting top-level await in script mode, but I can’t find it and it probably wouldn’t be feasible anyway because it implies the whole script, which would otherwise be blocking, is async.
That said, nothing is preventing anyone from using type="module" (or .mjs) for uncompiled code. In fact I’m doing this on a project specifically to bootstrap on-the-fly ESBuild TypeScript compilation.