TL;DR - most dynamic languages allow most things to change at any time. So with a large codebase, it's hard to know where a particular something is getting cha

TL;DR - most dynamic languages allow most things to change at any time. So with a large codebase, it's hard to know where a particular something is getting changed (or not). IOTW, it makes error traceability of the codebase more difficult.