I guess it's a design decision, I guess it could have been designed differently, but I'm not really sure. Doing it differently could very well break other thing

I guess it's a design decision, I guess it could have been designed differently, but I'm not really sure. Doing it differently could very well break other things that people do rely on. Referring to the original variables instead of making copies does save memory though: in your example there were 5 functions that each would have their own copy, instead of only 1 instance shared between them.