If the monster this card targets leaves the field and this card is rendered meaningless, you can use it for effects that need Trap Cards to be used like
This card can prevent your opponent's "Ultimate Tyranno" from attacking, and locking your opponent's other monsters' attacks.
This card is an excellent counter to use against powerful monsters when they're Summoned because your opponent cannot use cards that resurrect them from the Graveyard or removed from play zone. Sometimes, it is better to leave powerful monsters on the field than let them sit in the Graveyard or removed from play zone.
"Gravelstorm" can recycle this card (and blow away an opponent's Spell/Trap at the same time) when it is rendered useless due to the targeted monster being removed from the field (ways other than destruction i.e. Tribute Summon).
