You are forgetting that even Eich didn't want to do JS; he wanted to embed Scheme but was overruled by suits at Netscape who wanted to ride the Java hype. That's why the semicolons and curly braces. It really is indefensible on technical grounds.
Linters have been around for over a decade and solve all of these issues (as they do in other languages as well). They're also easily integrated in every text editor and build system I've ever seen.
And why shouldn't the interpreter support these rules? Because a linter can do this almost as easily, and not break backward compatibility.
That didn't stop people from wanting to come up with or use different languages in place of C, where possible.