Their ability to make Dragons when a creature deals damage the same turn it hits the board is perfect for a Ninja deck
Exquisite Blood means you gain life whenever an opponent loses it
In the right deck, they often cost just 1 blue mana
There are also a wide range of helpful Artifacts, including Equipment, Vehicles, or just general support ones like Lunatic Pandora which can be used to destroy one of your opponent's cards
Lands that become staples are often very expensive because of how easy it is to include them in multiple decks, and Bloomburrow brings two new contenders that I foresee following this exact trajectory
Set Boosters are also a great way to adventure through the plane of Dominaria, as all the common and uncommon cards are connected to each other, and they help tell the story of the invasion and defense of this glorious plane