There are junglers who can jungle okay without it, but having no smite on your team for objective control is awful. Therefore all junglers need to take smite. --- FACT: Four out of five people are crushed to death by giant diamonds every day.
Yes, there are. But the biggest reason you take smite is to guarantee that you can last-hit things like buff monsters, dragon, and baron. Let's say you don't have smite but the other team does. Near the end of the game you're doing Baron, and if the enemy team sees you doing it, their jungler can waltz in and drop an 800 damage bomb on Baron to kill it before you can. --- And then John was a zombie.