Also, probably some React developers would like to use TS/Flow and their manager says 'nope'.
I wish browsers would suck in TS directly. It doesn’t require much translation to get the corresponding JS files, just ignoring some types and that’s it.
It's pretty simple to get TS building via webpack for react, and tsc itself has a watch mode. The only PITA there is if you save any breaking changes, the build will obviously fail until you've completed and saved any the working changes, but at least you can't forget.
Typescript also isn't a very fast compiler, it doesn't seem to be incremental or retained at all, so when you build your project, it take a few seconds when your project has grown beyond a certain size. Sometimes I build and then hit run too early (before the build is actually finished).
Are you doing all of your TS dev in Visual Studio as well?