I can't quite tell from your tone if you're implying that this is a bad thing, or if you're of the opinion that Congress is shirking on their duties when they do this. I read it like, "'Congress just LOVES to pass vague laws so others have to step in' /sarcasm." My apologies if I'm misreading your tone.
For posterity, just to be clear, this is definitely a good thing here. In the case of, for example, the environment, which this post is about: Members of Congress are not experts in every field, so it makes more sense to pass a law called the Clean Air Act requiring protection of the air with some parameters, and then letting the experts at EPA fill in the details. In this case at least, it's not Congress shirking their duties, but rather the way it should work. i.e. Congress issues laws requiring general things, and the experts at the various federal agencies fill in the details with regulations (though obviously it doesn't always work perfectly).