Data centers have seen a lot of change in a short time. It used to be possible for organizations to run their service from a single data center and house their Domain Name Service (DNS) servers within it. It wasn’t an issue to have them in the same place, since if the data center went down, the DNS servers wouldn’t be of any use.
Of course, things aren’t so simple now. Organizations use multiple data centers, sometimes in multiple countries, not to mention cloud regions and highly distributed networks. Consequently, your DNS needs to be just as highly distributed as your content. After all, what good is a Disaster Recovery site if you have no way to direct your users to it?