Why can't Python have transpilers like JS does? Adding types to Python like Typescript could be a good thing.
People that want to write code that runs in a Web browser are locked in to Javascript, so they're "locked in" to JS; I can't think of a platform where the only option is to use Python.
babeljs for example used to be called `6to5` so i don't think it's lockin that causes this desire, but it's certainly true that the options for clientside programming languages that are widely deployed are fairly slim. i don't think they're related though.