Reveal it You must reveal the card before it hits your hand: as you draw it , before it joins the rest of your cards
You can put a land card onto the battlefield this way even if you've already played a land for the turn
Now if the UG lands player doesn't have a sufficient landfall threat on the board, he or she can still find value in returning their lands to hand, discarding them for value (maybe to Wild Mongrel, Noose Constrictor, etc., or Turntimber Sower, if not Trade Routes), and having options to re-play them for future landfall triggers or other shenanigans
Finally, you can spend six loyalty to create a 6/6 Green Wurm token for each Land you control, which is by far the nicest
Black has always had its share of powerful cards throughout MTGs history, be it powerful Alpha cards like Dark Ritual and Demonic Tutor or more recent cards like Grief and Archon of Cruelty