I don't consider it a foresight issue. I'm a believer in putting the burden on the caller not the callee. If I expect 0 and you have "0", it's your job to call parseInt(), not my job to branch out some if statements for type checking and coercion. For a few reasons:

1) debugging someone else's code is a lot more time consuming than debugging your own

2) actually fixing a bug in someone else's code means a pull request to someone who may not actively maintain that code

3) the docs are simpler to write and easier to read.

It's my only pain point with the JS community. The "give me whatever and I'll see if I can handle it for you" mentality:

  function doStuff(a, b, c) {

      if (!c && b instanceof Function) {
          c = b;
      }
      c()
  }

I'd rather be expressly told what to give you than try to read a wall of if statements in both the docs and your code.