Learning a new framework is intimidating enough without potentially having to learn a new language on top of it. I work in the news business, among people who in many cases learned the bare minimum of JavaScript necessary to visualise data and tell interactive stories, so that's my natural constituency — beginner-to-intermediate/casual programmers, most of whom don't even know what TypeScript is.

There are TS-first frameworks, such as Angular, and they're off-putting to people who just want to build something.