take the RoL/Hope deck as an example:
your hand is clogged up with loads of useless junk, your hope is not powered enough and you need to fractal more RoLs
you use this card and you hopefully swap your cards for pillars which you can get rid of instantly.
Or it is because you are waiting for a certain card e.g. Hope. you're about to be pwned by an FG and you need to refresh the cards in your hand
maybe you have 7 cards in your hand and you use this spell and there is 7/(total cards you still have in deck) chance to get the card you want e.g. Hope,
instead of waiting a few turns and get a 1/(total cards you still have in deck) chance to get Hope as you only draw on card each turn
Then you get pwned... and you wish this card was added in the game
this is just an example, i kno entropy cards dont go too well with the RoL/Hope deck.