You generally want to draw a card this frequently for one of two reasons: either the card is necessary for the fundamental functioning of the archetype, or the card is good to draw at every single point in the game
Like the scene sticks in your mind, it's great for mana storage
4 of each foil land, sets may vary.
The Ur-Dragon makes other Dragons cheaper, Edgar Markov creates Vampire tokens, Arahbo buffs a Cat, Inalla copies Wizard tokens, and Sidar lets you loot (draw and discard a card)
For Keruga, the Macrosage, that constraint is not including any one- or two-cost cards in your deck
Beetle based people could exist as an "everyman" race with a presence in all mana colors, and cockroaches ...would still be little pests that none of the insectoids particularly like, albeit just a little bigger, filling the roles other sets reserve for rats