The creative had to embrace this core concept
Its not necessary, though
To be fair, none of these decks are even close to competitive, but cards like Koma, Cosmos Serpent, Academy Manufactor, and Chulane, Teller of Tales are certainly in a league above what you usually expect from a precon (yes I know Chulane was the commander of its own precon)
Put the rest on the bottom of your library in a random order." On top of that, it also costs one less mana to cast for each artifact you control, which means it could be as low as two mana if you've got enough artifacts in play
In black, using Bargain should be easy to make Candy Grapple an all-star removal card that can hit nearly any creature in the deck aside from massive finishers in green like Hamlet Glutton
Did I miss your favorite one