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
Cards like Treacherous Blessing and Demonic Lore normally have huge downsides, but with Braids you can get your card draw and sacrifice them on your end step to avoid losing too much life and draw extra cards with her ability
Like the scene sticks in your mind, it's great for mana storage
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)
The design team then added flash, because the effect would need to be used on the opponent's turn
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