At least two reasons, Ralphie-boy. 1 to avoid rewriting all of your code when the perl-6 spec changes or Rakudo breaks backwards compatibility yet again. 2 to avoid having to depend on whatever the flavor du jour VM is THIS month.
Maybe that's just one reason. To prevent the beer-obsessed attention deficit development process of perl-6 from breaking your production code.
Of course that means you're right. You won't hear me say this often, Ralphie-boy, but you're right. There's no point. Why not just use a language that exists? One with developers who know how to deliver working software that doesn't break every month? Good point.