@Registered Anon  
That would take a really long time though! Usually the discard is relatively small and all the cards that are in it have been seen before, so it’s not going to take that long to look through it.
 
If you search through the draw deck, you don’t know what’s in it, plus it makes the game more opaque to newer players who don’t have every card memorized yet. (Even more than Changelings already do).
 
Also I’d hope (hypothetically) you were forced to reshuffle, otherwise you could just stack the deck.

So this lets you copy a power from the discard pile. Interesting. There should be a card that lets you power of a card from the draw deck, and (maybe) reshuffle the deck.