Blue players need something to finish the game, and control is generally how they stall long enough to draw a combination of cards that gives them a win in one fell swoop
Being able to draw cards upon playing or copying your spells is big game, as Wizard decks always want to have several answers in hand lest their foes aim to quash their well-laid plans
This is also the exact reason the sideboard is available
This mechanical loop looks like this: WB and BG overlap with put into exile triggers BG and GU overlap with late game mana cards GU and UW overlap with wanting low mana value creatures on the board RW and UW overlap in wanting creatures that werent cast RB and RW overlap with wanting to cast artifacts RB and UB overlap with wanting noncreature permanent cards to enter your graveyard UB and UR overlap in rewarding bouncing your own creatures UR and RG overlap in protecting attackers RG and GW overlap in wanting very large creatures GW and WB overlap in wanting to not cast spells This set of overlaps doesnt want a lot of cards to represent it
Organization is often undervalued but rarely unjustified. Frasio, royal archivist Illustrated by Howard Lyon Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Legal Modern Not Legal Brawl Legal Legacy Legal Comp
It also works wonders in extra turn decks like Aurelia, the Warleader, where you can create a strong threat and hit two consecutive times