A lot of it is culture, but I feel that culture fuels itself with the tricks available in the language. It just feels so clever to use the return value of `i++` - number of lines matters one-level down in ASM, so why not here. And things like `if (!i)` are quite cute, while being hard to aggregate unions of existing types, so return-value definitions especially tend to stay informal.

You're right about my analysis applying to all weakly typed languages, or at least languages with weakly-typed core functions. Python pretty much only brings memory safety to the table (which as I said in a sibling comment has an actual overhead so I didn't touch upon it here). But it does show that the Tarsnap and the Apple bug are caused by syntax, which is a pretty heavy indictment.