Let's say we have a hosting service for users who bring their own domain name. In this scenario we'd like to be able to service customers no matter who manages their DNS records. Be it GoDaddy, Namecheap, Google, Hostgator, some offshore place, etc.
At the same time, we'd also like to provide Load balancing so no one-user can overload any of our systems. This means, instead of having a customer's domain name point directly to the system where their webserver or app resides, it will point the HTTP connection to a Load Balancer which is prepared to handle serious connection