One of the major reasons all these kinds of services use javascript is that it can be reliably sandboxed (it needs to be, so it can run in a browser without eve

One of the major reasons all these kinds of services use javascript is that it can be reliably sandboxed (it needs to be, so it can run in a browser without every random website getting control of your machine). While there's nothing in theory preventing you from doing a similar thing with python, an implementation with the same hardening just doesn't exist. CPython sandboxes have been broken over and over again, to the point that conventional wisdom is "the only way to sandbox python is to run it in a VM". The only other language I can think of offhand that has similar levels of sandboxing is Lua.