Rooting gives you full access to the hardware. Technically, very few people had to root the Vox since you could sideload apps without full access. Yet a lot of people decided that the convenience of using Google Play made it worth the trouble of rooting it. As kcarscadden mentioned, the latest update includes Google Play so very few people remain interested in rooting the Vox.

Which is just as well since, to my knowledge, the only way to root the Vox with the latest update involves a screwdriver and a computer running Linux. It isn't for the faint of heart, but it is doable.

(The other reason to root the Vox is to remove some of the third party apps that Kobo ships on the Vox.)