The main point though, is that running Python in the browser it's an unnecessary abstraction because you get a crappier version of something that runs pretty we

The main point though, is that running Python in the browser it's an unnecessary abstraction because you get a crappier version of something that runs pretty well natively. If you're starting from scratch, I think that the browser might be close to native performance in some tasks. Porting existing applications is a pain when you start looking into the details.