Why doesn't Harpie's Hunting Ground allow you to destroy Enemy Controller cards that are set?? I know they are quick play, but the text on Harpie's Hunting Ground states, "destroy that target." Not - "destroy that target unless it's a quick play spell." Am I missing something? Or is this card broken?
Chaining is usually optional, unless a card specifies its owner must chain to it.
In E-Con's case, your opponent can let De-Spell destroy E-Con, instead of chaining to it.
Usually because there is no monster on your side of the field, or because your opponent thinks it's useless to activate it under current situation, and the S/T zone can be used for a better card that fits the situation more.