I suspect it is exactly that simple. It's just what we're used to. However I do have a lot of sympathy with the argument (as here) that one shouldn't use an er

I suspect it is exactly that simple. It's just what we're used to. However I do have a lot of sympathy with the argument (as here) that one shouldn't use an error recovery mechanism for stylistic effect. Automatic semicolon insertion is for fixing mistakes.