The only reason I can see is flavor.
In the meta, if you want to play past turn 6, you have to clear or nearly clear the board EVERY. SINGLE. TURN. If you miss one turn of clears it likely spells out a loss.
So how in the hell are you supposed to drop 6 mana on a card like Harth? If not on curve then when? When both you and your opponent are in fatigue?
I really want Harth to see play as its a throwback to a time when hearthstone was actually fun, but, ironically, the current toxic form of hearthstone basically makes playing the card impossible. Well, not exactly, you can play the card turn 6, waste your turn to see what cool hand you get, then you will die the next turn. But at least you can see what fun used to look like, right?