These can be a variety of shapes, colors, and styles which adds or subtracts value from a card
And a Negate is never useless later in the game as a top deck, unlike the Modal lands where a tapped land wasn't that heavily desired later and the spell isn't playable
They may think youre holding a crucial spell or waiting for you to block the way theyre expected to
Likewise, the Mythic Rare card, The Deck of Many Things, can literally win you the game if you hit that magical 20 in a d20 roll
Be sure to pack all the supplies you will need during this trip to Ravnica
There are no inherent benefits to having two specific colors in a deck outside of those colors' commonly used gimmicks - so Inking more cards for Sapphire, drawing more cards for Amethyst, having more Singer characters for Amber, and so on