Most represent the ability to get a two for one if they can do something worth a card and survive
Up the Beanstalk: This two-mana enchantment was simply the best card-drawing engine in Standard, fueling powerful midrange strategies
These cards serve valuable utility in Dimir reanimator decks in Legacy, which use blues unmatched stack interaction with blacks hand disruption and Reanimate, which is trivial to set up with pieces like Entomb or Troll of Khazad-dm, or even targeting yourself with Thoughtseize
As they cast it, that creature stops being prepared
Final Thoughts
This is especially popular for powered cubes, vintage cubes, dual lands, reserve list staples, and highly optimized Commander environments where replacement costs can become extremely high