Apropos that (though a bit OT) : what exactly is the deal with unescaped parantheses in bash?

They just seem to produce a syntax error no matter where I use them. But if they have no purpose, then why not simply treat them as nonspecial characters?

E.g.

  echo hello :-) ;

is invalid syntax, even though it doesn't seem to cause any ambiguities with any other bash syntax features. Why not just allow this and treat it like

  echo "hello" ":-)";

?