The best case scenario I can think of (that will be reasonably common, anyway) is when you cast some sort of instant or sorcery, someone tries to counter it, and then you get to cast this to double up on that original spell while nullifying the threat
Using an indestructible creature to block a lifelinker will still result in the opponent gaining life, and blocking a creature with wither will still cause -1/-1 counters to be placed on your creature (which could actually kill it!)
If you want something cleaner, you can print full card fronts at home and trim them properly
Normal versions of that artwork are going for $30 and up, while Shatter Foils are well over $100
The most common need for a mulligan with this deck is because you open a hand that relies on casting multiple spells with double white in the casting cost, but dont yet have the mana to do so
Yano even claimed that the reactions at one point constituted a moral panic