flametitan
Explorer
Why rolling a DC? Mostly because that's how the books present things and that's what the players seem to expect, to point of declaring skill rolls before even consulting me.
As Iserith would say, that's a bad thing. They should never roll before you tell them what to roll, or if they even should roll. Discourage the habit. Perhaps even outright tell them that they should maybe be a little less gung-ho about rolling.