It doesn’t require anything from the host

I don’t think the answer is that easy. Python is typically run on the server and JavaScript is client-side, which means that the incentives are aligned to optimize Python rather than JavaScript. I think investment in each follows and the difference is more that JavaScript runs in an isolated environment with a more flexible runtime.

Because it is a well documented source of bias.

With a Chromebook, there is one thing to lock down. On a Mac, there are a lot of things to do, because the whole point of it is that it's a normal computer.

Most schools will let you do all of those things, either out of incompetence or because it makes it impossible to actually use the Mac for what the Mac is good at.