Just because you're all-in on your favorite tribe doesn't mean you'll be able to rebuild if another player wipes the board and your army is swept into the graveyard
You can often choose from various shipping options, from standard to expedited
If you can outcast your opponents and get down to one or fewer cards in your hand, then you can refill your hand and out-card your opponents in the long run
You can not only prevent lifegain for your opponents, but you could also put a land onto the battlefield, give you creatures +1/+1 and reach, or deal three damage to each opponent at the same time
Yes, drawing this later in the game makes it a lot worse, but assuming youre a slow, controlling deck, you should still be able to use this effectively
Kill a creature and destroy a 'walker