Deck A has access to 40 percent of the cards, while Deck B has access to 20 percent of the cards
Think of it like using Act of Treason to grab a creature, attacking with it, and then tossing it into something like Goblin Bombardment or Deadly Dispute
The creature you use it on generally already has to be fairly impressive for it to be worthwhile, and it wont even always allow you to win combat if your creature isnt big enough
For example, if a chase card sells for $50 but only appears in about 1 in 50 packs, you could easily spend well over $50 on packs without ever pulling it
On top of that, there are plenty of other cards that work well for Ambers teamwork game plan
There is an occasional exception to that as a few of the APs remaining from very early editions were signed with a silver pen