This is perhaps because, without spending money, it will take close to two years to collect every card in just the first set
Can my opponent attempt to activate Entirely Normal Armchair if they don't know where it is or even if there's one on the battlefield
In the current meta many players use the same hand traps like Maxx C, making this a way to negate its activation
Creature theft effects and bounce effects make it so that running a card as suboptimal as Fowl Play shouldnt be necessary even if it has an occasional nice interaction, like turning an Elesh Norn or Griselbrand into a Chicken where stealing/bouncing it may have caused you to lose
The new Oblivion Ring gives decks with white but not blue access to this effect, which is likely to be desirable in a world of enchantments, Gods, and planeswalkers
That means that you can count on a 50-100% bump in the expected price range at each rarity, especially for the key cards that are wanted in multiples by players in multiple formats