Drawing more cards allows you to hit the key pieces you need more often whether thats removal, recursion, or even ramp
Even if Commander is all about shooting for the moon by casting big spells and assembling contraptions (figurative ones, not the Un-card type), Magic is still largely about playing creatures to the board
It was competitive with the colored four drops, and my second major deck used it as its four drop despite being three colors - and a control deck
Makes any permanent, including lands: trigger card draw from enchantresses, buf Yavimaya Enchantress / Ancestral Mask / Tuvasa the Sunlit
So if I make my commander Captain America, First Avenger (a red-white-blue creature), I cannot use any green or black cards while building that deck